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Cambridge IGCSE 0580/41, May/June 2024: Worked Solutions, Questions 5 to 9

Sir Faraz Hassan

Sir Faraz Hassan

16 Sept 2026

Table of Contents
    Cambridge IGCSE Mathematics (0580)0580/41 - Extended - May/June 2024130 marks  ·  2 hours 30 minutes  ·  Calculator allowed
    Back to questions 1 to 4

    This is the rest of the paper. Questions 1 to 4, the paper's overview and the frequently asked questions are on the first page.

    Original worked solutions for Cambridge IGCSE Mathematics, Paper 0580/41 (Extended), May/June 2024 series, sat Tuesday 7 May 2024 in Cambridge administrative zone 2130 marks, 2 hours 30 minutes, calculator allowed. The questions have been reworded; all numerical values match the original paper. The official question paper and mark scheme are published by Cambridge Assessment International Education. This resource reproduces neither the exam paper nor the official mark scheme.
    Cambridge sits this paper on different days in different administrative zones. The date above is the one published for Zone 2; timetables for the other zones of this series are no longer available from Cambridge.
    Both are PDF files hosted by Cambridge: official question paper (PDF) and official mark scheme (PDF).

    Try each question yourself first, then open the worked solution to check your method and see exactly where each method mark (M1) and independent mark (B1) is earned. The questions follow the same order as the original paper and carry the same marks.

    Download printable PDF

    All 9 questions with a full worked solution and mark scheme - free PDF

    Worked solutions, questions 5 to 9 of 9

    Question 5, Calculator allowed

    (a) The point PP has coordinates (1,7)(1, 7).
    The point QQ has coordinates (5,5)(5, -5).

    yxOPQNOT TOSCALE

    (i) What is PQ\overrightarrow{PQ}? [2 marks]

    (ii) Show that OP|\overrightarrow{OP}| and OQ|\overrightarrow{OQ}| are equal. [3 marks]

    (iii) A circle with centre OO has PQPQ as a chord.
    Work out this circle's circumference. [2 marks]

    (iv) A different circle, with centre RR, has PQPQ as its diameter.
    What are the coordinates of RR? [2 marks]

    (v) What is the equation of the perpendicular bisector of PQPQ?
    Give your answer in the form y=mx+cy = mx + c. [4 marks]

    (b) Point AA has position vector a\mathbf{a}.
    Point BB has position vector b\mathbf{b}.

    MM lies on ABAB, and AM:MB=2:3AM : MB = 2 : 3.

    In terms of a\mathbf{a} and b\mathbf{b}, what is the position vector of MM?
    Give your answer in its simplest form. [4 marks]

    (a)(i)(a)(iii)(a)(iv)(a)(v) y =(b)
    [Total 17 marks]
    Show solution & mark schemeHide solution & mark scheme

    Question 5 - Exam Solution

    Understanding the Question
    Given
    P(1,7)P(1, 7) and Q(5,5)Q(5, -5), with OO the origin.
    A circle centred on OO with PQPQ as a chord, and a second circle with PQPQ as its diameter and RR as its centre.
    Position vectors a\mathbf{a} and b\mathbf{b}, with MM on ABAB and AM:MB=2:3AM : MB = 2 : 3.
    Find
    PQ\overrightarrow{PQ}, and a demonstration that OP|\overrightarrow{OP}| and OQ|\overrightarrow{OQ}| are the same length. The circumference of the circle centred on OO, the coordinates of RR, and the perpendicular bisector of PQPQ in the form y=mx+cy = mx + c. OM\overrightarrow{OM} in terms of a\mathbf{a} and b\mathbf{b}.
    Plan the Solution
    • Subtract position vectors for PQ\overrightarrow{PQ}, then use x2+y2\sqrt{x^2 + y^2} for each distance from the origin.
    • PP and QQ both lie on the circle centred OO, so that common distance is its radius and the circumference follows.
    • The centre of a circle is halfway along any diameter, so RR is the midpoint of PQPQ.
    • The perpendicular bisector goes through that midpoint with the negative reciprocal of the gradient of PQPQ.
    • For part (b), go from OO to AA and then part of the way along ABAB; a ratio of 2:32 : 3 makes that part 25\dfrac{2}{5}.
    Worked Solution [17 marks]
    Rule - Vectors and coordinate geometry: PQ=OQOP\overrightarrow{PQ} = \overrightarrow{OQ} - \overrightarrow{OP}, a point's distance from the origin is x2+y2\sqrt{x^2 + y^2}, the midpoint of a segment is the average of its ends, and perpendicular gradients multiply to 1-1.
    (a)(i) Subtract the position vectors
    PQ=OQOP\overrightarrow{PQ} = \overrightarrow{OQ} - \overrightarrow{OP}
    PQ=(55)(17)=(412)\overrightarrow{PQ} = \begin{pmatrix} 5 \\ -5 \end{pmatrix} - \begin{pmatrix} 1 \\ 7 \end{pmatrix} = \begin{pmatrix} 4 \\ -12 \end{pmatrix}
    (Reason: The vector from PP to QQ is where you finish minus where you start, taken one component at a time.)
    (a)(ii) The distance of PP from the origin
    OP=12+72=1+49=50|\overrightarrow{OP}| = \sqrt{1^2 + 7^2} = \sqrt{1 + 49} = \sqrt{50}
    (Reason: Pythagoras on the right-angled triangle whose two shorter sides are the coordinates of PP.)
    (a)(ii) The distance of QQ from the origin
    OQ=52+(5)2=25+25=50|\overrightarrow{OQ}| = \sqrt{5^2 + (-5)^2} = \sqrt{25 + 25} = \sqrt{50}
    (Reason: Squaring removes the sign, so a yy-coordinate of 5-5 contributes 2525 just as 55 would. Both magnitudes come out as 50\sqrt{50}, which is what this part asks you to show.)
    (a)(iii) The radius of the circle centred OO
    r=OP=OQ=50r = |\overrightarrow{OP}| = |\overrightarrow{OQ}| = \sqrt{50}
    (Reason: PQPQ is a chord, so PP and QQ sit on the circle and OPOP and OQOQ are both radii. Part (ii) has already shown they are equal.)
    (a)(iii) Apply the circumference formula
    C=2×π×rC = 2 \times \pi \times r
    C=2×π×50=44.4288C = 2 \times \pi \times \sqrt{50} = 44.4288\ldots
    (Reason: Keep the surd in the calculator instead of rounding the radius first, or the last figure drifts.)
    (a)(iii) Round the circumference
    C=44.4C = 44.4
    (Reason: A calculated length is given to three significant figures unless the question says otherwise, and 44.428844.4288\ldots rounds to 44.444.4.)
    (a)(iv) RR is the midpoint of PQPQ
    R=(1+52,7+(5)2)=(3,1)R = \left( \dfrac{1 + 5}{2}, \dfrac{7 + (-5)}{2} \right) = (3, 1)
    (Reason: The centre of a circle sits halfway along any diameter, so average the xx-coordinates and average the yy-coordinates.)
    (a)(v) The gradient of PQPQ
    7(5)15=124=3\dfrac{7 - (-5)}{1 - 5} = \dfrac{12}{-4} = -3
    (Reason: Rise over run, taking PP first on the top and on the bottom so the two subtractions match.)
    (a)(v) The perpendicular gradient
    13=13\dfrac{-1}{-3} = \dfrac{1}{3}
    (Reason: Perpendicular gradients multiply to 1-1, so turn the gradient upside down and change its sign.)
    (a)(v) Fit the line through RR
    1=13×3+c1 = \dfrac{1}{3} \times 3 + c
    c=0c = 0
    y=13xy = \dfrac{1}{3}x
    (Reason: A bisector cuts PQPQ at its midpoint, so R(3,1)R(3, 1) lies on it. Here the constant works out as zero, so the line passes through the origin.)
    (b) The step from AA to MM
    AB=ba\overrightarrow{AB} = \mathbf{b} - \mathbf{a}
    AM=22+3AB=25(ba)\overrightarrow{AM} = \dfrac{2}{2 + 3}\overrightarrow{AB} = \dfrac{2}{5}(\mathbf{b} - \mathbf{a})
    (Reason: A ratio of 2:32 : 3 splits ABAB into 55 equal parts, and MM stands after 22 of them.)
    (b) Travel from OO to MM
    OM=OA+AM\overrightarrow{OM} = \overrightarrow{OA} + \overrightarrow{AM}
    OM=a+25(ba)=35a+25b\overrightarrow{OM} = \mathbf{a} + \dfrac{2}{5}(\mathbf{b} - \mathbf{a}) = \dfrac{3}{5}\mathbf{a} + \dfrac{2}{5}\mathbf{b}
    (Reason: Collecting the a\mathbf{a} terms gives 125=351 - \dfrac{2}{5} = \dfrac{3}{5}, and that collecting is what makes it the simplest form.)
    (a)(i) PQ=(412)\overrightarrow{PQ} = \begin{pmatrix} 4 \\ -12 \end{pmatrix}(a)(ii) OP=OQ=50|\overrightarrow{OP}| = |\overrightarrow{OQ}| = \sqrt{50}(a)(iii) 44.444.4(a)(iv) R=(3,1)R = (3, 1)(a)(v) y=13xy = \dfrac{1}{3}x(b) OM=35a+25b\overrightarrow{OM} = \dfrac{3}{5}\mathbf{a} + \dfrac{2}{5}\mathbf{b}
    Verification
    Check 1: Put x=3x = 3 into the bisector and see whether it reaches RR. 33=1\dfrac{3}{3} = 1, so (3,1)(3, 1) is on the line.
    Check 2: Measure RR against both ends of the diameter. RP=22+62=40RP = \sqrt{2^2 + 6^2} = \sqrt{40} and RQ=22+62=40RQ = \sqrt{2^2 + 6^2} = \sqrt{40}, equal as a centre requires.
    Check 3: Work the circumference the other way round, from the diameter. 2×50=14.14212 \times \sqrt{50} = 14.1421\ldots and π×14.1421=44.4288\pi \times 14.1421\ldots = 44.4288\ldots, which matches.
    Check 4: A point ON the line ABAB has coefficients adding to 11. 35+25=1\dfrac{3}{5} + \dfrac{2}{5} = 1, so MM is on ABAB and not off it.
    Mark Scheme Breakdown
    StepMarkDescriptionGot it?
    (a)(i) PQ\overrightarrow{PQ} as a column vectorNoteThe Answer column gives the column vector with 44 above 12-12, and the Marks column gives 22 for it.
    (a)(i) Each component of PQ\overrightarrow{PQ}B1For each.
    (a)(ii) The sum of squares for OP\overrightarrow{OP}M1For 12+721^2 + 7^2.
    (a)(ii) The sum of squares for OQ\overrightarrow{OQ}M1For 52+([]5)25^2 + ([-]5)^2.
    (a)(ii) Both magnitudes equal 50\sqrt{50}A1Both 50\sqrt{50} oe.
    (a)(ii) The condition on the accuracy markNoteWith no errors seen.
    (a)(ii) The special case when nothing else is scoredSC1If M0M0A0 scored, for 50\sqrt{50} oe for each.
    (a)(iii) The circumferenceNoteThe Answer column gives 44.444.4 or 44.42[8]44.42[8\ldots] to 44.43544.435, and the Marks column gives 22 for it.
    (a)(iii) The follow-through allowedNoteFT their (a)(ii) correct to 3sf or better.
    (a)(iii) The method for the circumferenceM1For 2×π×their 502 \times \pi \times \text{their } \sqrt{50} oe.
    (a)(iv) The centre RRNoteThe Answer column gives (3,1)(3, 1), and the Marks column gives 22 for it.
    (a)(iv) Each coordinate of RRB1For each.
    (a)(v) The equation of the perpendicular bisectorNoteThe Answer column gives [y=]13x[y =] \dfrac{1}{3}x, and the Marks column gives 44 for it.
    (a)(v) A correct equation in the wrong formB3For a correct equation in the wrong form as final answer.
    (a)(v) The perpendicular gradient on its ownB2Or for 13\dfrac{1}{3} stated or used as perpendicular gradient.
    (a)(v) Second method: the gradient of PQPQM1Or for [grad PQ]=7515[\text{grad } PQ] = \dfrac{7 - -5}{1 - 5} oe.
    (a)(v) Second method: the negative reciprocalM1For 1their grad PQ\dfrac{-1}{\text{their grad } PQ}.
    (a)(v) Second method: substituting into y=mx+cy = mx + cM1depFor substituting their (a)(iv) or (0,0)(0, 0) into y=their mx+cy = \text{their } mx + c oe, dep on the 2nd M1 or B2.
    (b) The position vector of MMNoteThe Answer column gives 35a+25b\dfrac{3}{5}\mathbf{a} + \dfrac{2}{5}\mathbf{b} final answer, and the Marks column gives 44 for it.
    (b) An unsimplified correct answerB3For an unsimplified correct answer.
    (b) AM\overrightarrow{AM} or BM\overrightarrow{BM} in terms of a\mathbf{a} and b\mathbf{b}B2Or for AM=25(ba)AM = \dfrac{2}{5}(\mathbf{b} - \mathbf{a}) soi, or BM=35(ab)BM = \dfrac{3}{5}(\mathbf{a} - \mathbf{b}) soi.
    (b) AB\overrightarrow{AB}, a correct route, or a correct diagramB1Or for AB=baAB = \mathbf{b} - \mathbf{a} or BA=abBA = \mathbf{a} - \mathbf{b}, or for a correct route for OMOM, or for correct diagram.

    Full marks: 17/17

    Question 6, Calculator allowed

    The positions of two beacons AA and BB, a yacht CC and a marina HH are marked on the diagram.
    BB lies due west of CC.

    ABCHNorth11 km14 km32 km25°55°NOT TOSCALE

    (a) From yacht CC, what is the bearing of the marina? [1 mark]

    (b) (i) Show that the size of angle CBHCBH is 100100^\circ. [1 mark]

    (ii) Show that the length of BHBH is 13.713.7 km, correct to 11 decimal place. [3 marks]

    (c) What is the bearing of AA from BB? [5 marks]

    (d) Yacht CC leaves at 11 pm and sails the 3232 km straight to the marina, holding a speed of 1010 knots.

    (i) At what time does yacht CC reach the marina?
    Give this time correct to the nearest minute.
    [1 knot=1.852 km/h1 \text{ knot} = 1.852 \text{ km/h}] [4 marks]

    (ii) How far is yacht CC from the marina at the moment when it is closest to beacon BB? [3 marks]

    (a)(c)(d)(i)(d)(ii) km
    [Total 17 marks]
    Show solution & mark schemeHide solution & mark scheme

    Question 6 - Exam Solution

    Understanding the Question
    Given
    Two beacons AA and BB, a yacht CC and a marina HH, with BB due west of CC.
    AB=11AB = 11 km, AH=14AH = 14 km and HC=32HC = 32 km.
    Angle BCH=25BCH = 25^\circ and angle BHC=55BHC = 55^\circ.
    The yacht leaves at 11 pm at 1010 knots, and 11 knot is 1.8521.852 km/h.
    Find
    The bearing of the marina from the yacht, and a demonstration that angle CBHCBH is 100100^\circ and that BHBH is 13.713.7 km. The bearing of AA from BB. The arrival time, and the distance still to run when the yacht is nearest to BB.
    Plan the Solution
    • A bearing is measured clockwise from north, so start (a) from the 270270^\circ line that points from CC back to BB.
    • The angles of triangle BCHBCH add to 180180^\circ, which leaves the angle at BB.
    • Two angles and a side opposite one of them make triangle BCHBCH a sine-rule triangle.
    • Triangle ABHABH has all three sides known, so the cosine rule gives the angle at BB. Adding it to the bearing of HH from BB turns it into a bearing.
    • A knot is a nautical mile an hour, so convert the speed once and then divide distance by speed.
    • The shortest distance from BB to the yacht's track is the perpendicular, and that makes a right-angled triangle with BHBH as its hypotenuse.
    Worked Solution [17 marks]
    Rule - Bearings, the sine rule and the cosine rule: a bearing is measured clockwise from north and written with three figures, asinA=bsinB\dfrac{a}{\sin A} = \dfrac{b}{\sin B}, and a2=b2+c22bccosAa^2 = b^2 + c^2 - 2bc\cos A.
    (a) Turn round the line from CC to BB
    27025=245270 - 25 = 245
    (Reason: BB is due west of CC, so from CC the beacon lies on a bearing of 270270^\circ. The marina sits 2525^\circ on the anticlockwise side of that line, so its bearing is 2525 less.)
    (b)(i) The angles of triangle BCHBCH
    180(55+25)=100180 - (55 + 25) = 100
    (Reason: The angles of any triangle add to 180180^\circ. The angles at HH and CC are given, so the one at BB is whatever is left.)
    (b)(ii) Set up the sine rule in triangle BCHBCH
    BHsin25=32sin100\dfrac{BH}{\sin 25} = \dfrac{32}{\sin 100}
    (Reason: BHBH is opposite the 2525^\circ angle and HCHC is opposite the 100100^\circ angle, so those are the two pairs that go together.)
    (b)(ii) Rearrange and work it out
    BH=32×sin25sin100BH = \dfrac{32 \times \sin 25}{\sin 100}
    BH=13.7324BH = 13.7324\ldots
    (Reason: Multiply both sides by sin25\sin 25. Keep every figure in the calculator instead of rounding here, or the first decimal place is not safe.)
    (b)(ii) Round to 11 decimal place
    BH=13.7BH = 13.7
    (Reason: The digit after the first decimal place is 33, so the 77 stays as it is, and that is the 13.713.7 km the question asks to be shown.)
    (c) The bearing of HH from BB
    90+100=19090 + 100 = 190
    (Reason: CC is due east of BB, so BCBC points along 090090^\circ. Turning clockwise through the 100100^\circ of angle CBHCBH lands on BHBH.)
    (c) The cosine rule in triangle ABHABH
    cosB=112+13.721422×11×13.7\cos B = \dfrac{11^2 + 13.7^2 - 14^2}{2 \times 11 \times 13.7}
    (Reason: All three sides are known, so the rearranged cosine rule gives the cosine of the angle at BB. The side that is subtracted is the one opposite that angle.)
    (c) Work out the top and the bottom
    112+13.72142=112.6911^2 + 13.7^2 - 14^2 = 112.69
    2×11×13.7=301.42 \times 11 \times 13.7 = 301.4
    (Reason: Square each side first, then combine the squares the way the rearranged rule sets them out.)
    (c) Divide, then take the inverse cosine
    112.69301.4=0.3739\dfrac{112.69}{301.4} = 0.3739
    cos1(0.3739)=68.0\cos^{-1}(0.3739) = 68.0\ldots
    (Reason: The calculator must be in degree mode. Angle ABHABH comes out as 68.068.0^\circ to 11 decimal place.)
    (c) Add the angle to the bearing of HH
    190+68.0=258.0190 + 68.0 = 258.0
    (Reason: AA lies on the far side of BHBH from CC, so the turn carries on clockwise past 190190^\circ. A bearing is written with three figures, so the answer is 258258^\circ.)
    (d)(i) Change the speed into km/h
    10×1.852=18.5210 \times 1.852 = 18.52
    (Reason: A knot is one nautical mile an hour, and the question gives 11 knot as 1.8521.852 km/h.)
    (d)(i) Divide the distance by the speed
    3218.52×60=103.67\dfrac{32}{18.52} \times 60 = 103.67
    (Reason: Distance over speed gives the time in hours, and the 6060 turns those hours straight into minutes.)
    (d)(i) Change the minutes into hours and minutes
    60+44=10460 + 44 = 104
    (Reason: 103.67103.67 minutes is 104104 minutes to the nearest minute, which is 11 hour and 4444 minutes. Starting at 11 pm, the yacht ties up at 2 442\ 44 pm.)
    (d)(ii) Find where the yacht passes closest to BB
    x13.7=cos55\dfrac{x}{13.7} = \cos 55
    (Reason: The shortest distance from a point to a line is the perpendicular, so drop one from BB onto CHCH and call the foot XX. In right-angled triangle BXHBXH the side HXHX is adjacent to the 5555^\circ angle and BHBH is the hypotenuse.)
    (d)(ii) Work out that distance
    x=13.7×cos55=7.858x = 13.7 \times \cos 55 = 7.858\ldots
    x=7.86x = 7.86
    (Reason: That is the stretch of CHCH still lying between the yacht and the marina, given to 33 significant figures.)
    (a) 245245^\circ(b)(i) angle CBHCBH is 100100^\circ(b)(ii) BHBH is 13.713.7 km(c) 258258^\circ(d)(i) 2 442\ 44 pm(d)(ii) 7.867.86 km
    Verification
    Check 1: Walk the bearings round the figure. The reverse of the bearing of HH from CC should lead back through the 5555^\circ angle to the reverse of 190190^\circ. 245180=65245 - 180 = 65, then 6555=1065 - 55 = 10, and the reverse of 190190^\circ is 190180=10190 - 180 = 10, which agrees.
    Check 2: Add all three angles of triangle BCHBCH. 25+55+100=18025 + 55 + 100 = 180, as a triangle requires.
    Check 3: Put the unrounded BHBH back into the sine rule and compare the two ratios. 13.7324sin25=32.49\dfrac{13.7324}{\sin 25} = 32.49\ldots and 32sin100=32.49\dfrac{32}{\sin 100} = 32.49\ldots, the same ratio.
    Check 4: Run the cosine rule the other way round, using the angle just found to rebuild AHAH. 112+13.722×11×13.7×cos68.04=196.011^2 + 13.7^2 - 2 \times 11 \times 13.7 \times \cos 68.04^\circ = 196.0\ldots, and 196=14\sqrt{196} = 14, which is AHAH.
    Check 5: Multiply the sailing time back by the speed. 18.52×1.7279=32.018.52 \times 1.7279 = 32.0 km, which is HCHC.
    Check 6: Test right-angled triangle BXHBXH with Pythagoras, where BX=13.7×sin55BX = 13.7 \times \sin 55. 11.22242+7.8582=187.6911.2224^2 + 7.858^2 = 187.69, and 13.72=187.6913.7^2 = 187.69, so the two sides do make up the hypotenuse.
    Mark Scheme Breakdown
    StepMarkDescriptionGot it?
    (a) The bearing of the marina from the yachtNoteThe Answer column gives 245245, and the Marks column gives 11 for it.
    (b)(i) The angle at BB from the angle sumM1For 180(55+25) [=100]180 - (55 + 25)\ [=100].
    (b)(ii) The sine rule rearranged for BHBHM2For 32×sin25sin100\dfrac{32 \times \sin 25}{\sin 100} oe.
    (b)(ii) The sine rule before it is rearrangedM1For sin25BH=sin10032\dfrac{\sin 25}{BH} = \dfrac{\sin 100}{32} oe.
    (b)(ii) The unrounded length of BHBHA1For 13.7313.73\ldots.
    (c) The bearing of AA from BBNoteThe Answer column gives 258258 or 257.9257.9 to 258.0258.0\ldots, and the Marks column gives 55 for it.
    (c) The angle at BB on its ownB4For 67.967.9 to 68.068.0\ldots.
    (c) Second method: the cosine rule rearranged for cosB\cos BM2Or for [cos=]112+13.721422×13.7×11[\cos =] \dfrac{11^2 + 13.7^2 - 14^2}{2 \times 13.7 \times 11}.
    (c) Second method: the value of the cosineA1For 0.37380.3738 to 0.3760.376.
    (c) Second method: the cosine rule before it is rearrangedM1Or for 142=112+13.722×11×13.7×cosB14^2 = 11^2 + 13.7^2 - 2 \times 11 \times 13.7 \times \cos B.
    (c) Turning the angle at BB into a bearingM1depFor 190+their angle B190 + \text{their angle } B, dep on at least M1.
    (d)(i) The arrival timeNoteThe Answer column gives 2 442\ 44 pm or 14 4414\ 44 cao, and the Marks column gives 44 for it.
    (d)(i) The journey time, as hours and minutes or as minutesB3For 1 hour 441 \text{ hour } 44 or 1 hour 43.61 \text{ hour } 43.6 to 1 hour 43.81 \text{ hour } 43.8 or 104104 or 103.6103.6 to 103.8103.8.
    (d)(i) The journey time in hoursB2Or for 1.7271.727 to 1.731.73.
    (d)(i) The method, taken as far as minutesM2Or for 3210×1.852×60\dfrac{32}{10 \times 1.852} \times 60.
    (d)(i) The method, taken only as far as hoursM1Or for 3210×1.852\dfrac{32}{10 \times 1.852}.
    (d)(ii) The distance still to runNoteThe Answer column gives 7.8577.857 to 7.887.88, and the Marks column gives 33 for it.
    (d)(ii) The trigonometry in the right-angled triangleM2For x13.7=cos55\dfrac{x}{13.7} = \cos 55 oe.
    (d)(ii) Recognising where the shortest distance fallsM1Or for dist to HH occurs when perpendicular from BB meets CHCH soi.

    Full marks: 17/17

    Question 7, Calculator allowed

    A crate in the shape of a cuboid is drawn above.
    The crate has no top.

    40 cm70 cm30 cmNOT TOSCALE

    (a) (i) What is the surface area of the inside of the open crate? [3 marks]

    (ii) Cylindrical tins, each of height 2020 cm and diameter 1515 cm, are put into the crate.
    What is the greatest number of these tins that fit completely inside the crate? [3 marks]

    (b) The mass of a solid bronze cone is 750750 g.
    The bronze has a density of 8.98.9 g/cm³.
    The radius and the height of the cone are in the ratio 1:31 : 3.

    (i) Show that the cone has a radius of 2.992.99 cm, correct to 33 significant figures.
    [Density=massvolume\text{Density} = \dfrac{\text{mass}}{\text{volume}}]
    [The volume, VV, of a cone with radius rr and height hh is V=13πr2hV = \dfrac{1}{3}\pi r^2 h.] [4 marks]

    (ii) What is the total surface area of the cone?
    [The curved surface area, AA, of a cone with radius rr and slant height ll is A=πrlA = \pi r l.] [5 marks]

    (a)(i) cm²(a)(ii)(b)(ii) cm²
    [Total 15 marks]
    Show solution & mark schemeHide solution & mark scheme

    Question 7 - Exam Solution

    Understanding the Question
    Given
    An open crate in the shape of a cuboid, 7070 cm long, 3030 cm deep and 4040 cm high, with no top.
    Tins that are cylinders of height 2020 cm and diameter 1515 cm.
    A solid bronze cone of mass 750750 g, made of bronze of density 8.98.9 g/cm³, whose radius and height are in the ratio 1:31 : 3.
    Find
    The surface area of the inside of the open crate, and the greatest number of tins that fit inside it. A demonstration that the cone has radius 2.992.99 cm, and then the total surface area of that cone.
    Plan the Solution
    • An open box has five faces, not six: a base and two matching pairs of walls.
    • A tin cannot be cut, so divide each edge of the crate by the measurement of the tin that lies along it and round every count down before multiplying.
    • Density ties mass to volume, so turn the 750750 g into a volume first.
    • The ratio makes the height 3r3r, and 13πr2×3r\dfrac{1}{3}\pi r^2 \times 3r collapses to πr3\pi r^3, which leaves one unknown in one equation.
    • The radius, the height and the slant height make a right-angled triangle, so Pythagoras gives ll before A=πrlA = \pi r l can be used.
    • A cone standing on its base has a flat circle as well as a curved surface, so the total is πrl+πr2\pi r l + \pi r^2.
    Worked Solution [15 marks]
    Rule - Surface area, density and the cone: an open box has five faces, density=massvolume\text{density} = \dfrac{\text{mass}}{\text{volume}}, V=13πr2hV = \dfrac{1}{3}\pi r^2 h and A=πrlA = \pi r l.
    (a)(i) The base of the crate
    70×30=210070 \times 30 = 2100
    (Reason: The crate stands on a rectangle 7070 cm by 3030 cm, and that face is inside the crate, so it is one of the faces counted.)
    (a)(i) The two end walls
    2×30×40=24002 \times 30 \times 40 = 2400
    (Reason: The two ends stand on the 3030 cm edges and rise the full 4040 cm. They are a matching pair, so one area is doubled.)
    (a)(i) The two long walls
    2×40×70=56002 \times 40 \times 70 = 5600
    (Reason: The other two walls stand on the 7070 cm edges and rise to the same height as the ends. They are a matching pair as well.)
    (a)(i) Add the five faces
    2100+2400+5600=101002100 + 2400 + 5600 = 10\,100
    (Reason: A base and four walls, with no lid to add. Every term is a length times a length, so the answer is in square centimetres.)
    (a)(ii) How many tins lie along the 7070 cm edge
    7015=4.66\dfrac{70}{15} = 4.66\ldots
    (Reason: Each tin needs 1515 cm of that edge. Four tins use 6060 cm and a fifth would need 7575 cm, so the count is 44 - part of a tin is no use.)
    (a)(ii) Across the crate, and up it
    3015=2\dfrac{30}{15} = 2
    4020=2\dfrac{40}{20} = 2
    (Reason: The tins stand upright, so it is the diameter that has to fit across the 3030 cm and the height of a tin that has to fit up the 4040 cm. Both of these divide exactly.)
    (a)(ii) Multiply the three counts
    4×2×2=164 \times 2 \times 2 = 16
    (Reason: Eight tins cover the base in a 44 by 22 block, and a second layer of eight stands on top of them.)
    (b)(i) Turn the mass into a volume
    V=7508.9=84.2696V = \dfrac{750}{8.9} = 84.2696\ldots
    (Reason: Density is mass divided by volume, so volume is mass divided by density. Keep every figure in the calculator here - rounding now would move the third significant figure of the radius.)
    (b)(i) Put the ratio into the cone formula
    h=3rh = 3r
    V=13πr2×3r=πr3V = \dfrac{1}{3}\pi r^2 \times 3r = \pi r^3
    (Reason: The ratio 1:31 : 3 makes the height three times the radius. The 33 and the 13\dfrac{1}{3} cancel, which leaves one unknown.)
    (b)(i) Solve for rr
    πr3=84.2696\pi r^3 = 84.2696\ldots
    r3=84.2696π=26.8238r^3 = \dfrac{84.2696\ldots}{\pi} = 26.8238\ldots
    r=26.82383=2.9934r = \sqrt[3]{26.8238\ldots} = 2.9934\ldots
    (Reason: Divide by π\pi, then take the cube root. Every figure is carried until the last line.)
    (b)(i) Round to 33 significant figures
    r=2.99r = 2.99
    (Reason: The fourth significant figure is 44, so the third stays as it is. That is the 2.992.99 cm the question asks to be shown.)
    (b)(ii) The height and the slant height
    h=3×2.99=8.97h = 3 \times 2.99 = 8.97
    2.992+8.972=89.4012.99^2 + 8.97^2 = 89.401
    l=89.401=9.4552l = \sqrt{89.401} = 9.4552\ldots
    (Reason: The radius, the height and the slant height make a right-angled triangle, with the slant height as its hypotenuse.)
    (b)(ii) The curved surface
    π×2.99×9.4552=88.816\pi \times 2.99 \times 9.4552 = 88.816
    (Reason: This is the formula the question gives, A=πrlA = \pi r l, with the radius and the slant height just found.)
    (b)(ii) The base circle
    π×2.992=28.086\pi \times 2.99^2 = 28.086
    (Reason: The cone is solid and stands on its base, so there is a flat circle of radius 2.992.99 cm to add as well.)
    (b)(ii) Add the two areas
    88.816+28.086=116.90288.816 + 28.086 = 116.902
    A=117A = 117
    (Reason: Rounded to 33 significant figures, the total surface area is 117117 cm².)
    (a)(i) 1010010\,100 cm²(a)(ii) 1616 tins(b)(i) the radius is 2.992.99 cm(b)(ii) 117117 cm²
    Verification
    Check 1: Build the four walls as one band round the base instead of adding them face by face. 2×(70+30)=2002 \times (70 + 30) = 200 cm round the base, 200×40=8000200 \times 40 = 8000 cm² of wall, and 8000+2100=101008000 + 2100 = 10\,100 cm² once the base is added.
    Check 2: Measure the space the tins take up inside the crate. 4×15=604 \times 15 = 60 cm of the 7070 cm, 2×15=302 \times 15 = 30 cm of the 3030 cm and 2×20=402 \times 20 = 40 cm of the 4040 cm. A fifth tin along the longest edge would need 7575 cm.
    Check 3: Put the unrounded radius back and rebuild the mass it came from. With r=2.9934r = 2.9934\ldots the volume πr3\pi r^3 is 84.269684.2696\ldots cm³, and 8.9×84.2696=7508.9 \times 84.2696\ldots = 750 g.
    Check 4: Rebuild the surface area a different way. For this cone l=r10l = r\sqrt{10}, so the total is πr2(1+10)\pi r^2 (1 + \sqrt{10}). 1+10=4.16231 + \sqrt{10} = 4.1623 and 28.086×4.1623=116.90228.086 \times 4.1623 = 116.902.
    Check 5: Is the size sensible? This cone is three times as tall as its radius, so the curved surface should be a few times the base circle. 88.81628.086=3.162\dfrac{88.816}{28.086} = 3.162, which is 10\sqrt{10} to 44 significant figures - the ratio lr\dfrac{l}{r} for this cone.
    Mark Scheme Breakdown
    StepMarkDescriptionGot it?
    (a)(i) The surface area of the inside of the crateNoteThe Answer column gives 1010010\,100, and the Marks column gives 33 for it.
    (a)(i) The five faces, all of themM2For 30×70+2×30×40+2×40×7030 \times 70 + 2 \times 30 \times 40 + 2 \times 40 \times 70.
    (a)(i) One face of the crate worked outM1Or for 30×4030 \times 40 or 30×7030 \times 70 or 40×7040 \times 70.
    (a)(ii) The greatest number of tinsNoteThe Answer column gives 1616, and the Marks column gives 33 for it.
    (a)(ii) How many tins fit along each edgeM2For 22 fit width, 22 fit height and 44 fit length soi.
    (a)(ii) One edge divided by one tinM1Or for 7070, 3030 or 4040 divided by 1515 or 2020.
    (b)(i) The volume equation, with the ratio already usedM2For 13πr2×3r=their 7508.9\dfrac{1}{3}\pi r^2 \times 3r = \text{their } \dfrac{750}{8.9} oe.
    (b)(i) The density formula used on the two given valuesM1For using 750750 and 8.98.9 correctly in v=mdv = \dfrac{m}{d} oe or 7508.9\dfrac{750}{8.9}.
    (b)(i) The cube of the radius made the subjectM1depFor r3=their (7508.9)πr^3 = \dfrac{\text{their }\left(\dfrac{750}{8.9}\right)}{\pi} oe.
    (b)(i) The unrounded radiusA1For r=2.993r = 2.993\ldots.
    (b)(ii) The total surface area of the coneNoteThe Answer column gives 117117 or 116.9116.9 to 117.2117.2, and the Marks column gives 55 for it.
    (b)(ii) Both surfaces in one expressionM4For π×2.992+π×2.99×2.992+(3×2.99)2\pi \times 2.99^2 + \pi \times 2.99 \times \sqrt{2.99^2 + (3 \times 2.99)^2} oe.
    (b)(ii) The curved surface area on its ownM3Or for π×2.99×2.992+(3×2.99)2\pi \times 2.99 \times \sqrt{2.99^2 + (3 \times 2.99)^2}.
    (b)(ii) The slant heightM2Or for 2.992+(3×2.99)2\sqrt{2.99^2 + (3 \times 2.99)^2}.
    (b)(ii) Pythagoras started, or the base circle aloneM1Or for 2.992+(3×2.99)22.99^2 + (3 \times 2.99)^2, or for π×2.992\pi \times 2.99^2.

    Full marks: 15/15

    Question 8, Calculator allowed

    (a) Sketch the graph of y=x2+7x18y = x^2 + 7x - 18 on the axes below.
    The values where the graph meets the xx-axis and the yy-axis must be written on your sketch. [4 marks]

    yxO

    (b) (i) What is the derivative of y=x23x28y = x^2 - 3x - 28? [2 marks]

    (ii) For y=x23x28y = x^2 - 3x - 28, give the coordinates of the turning point. [3 marks]

    (c) The graph of y=x23x28y = x^2 - 3x - 28 is intersected by the line y=52xy = 5 - 2x at point PP and point QQ.

    What are the coordinates of PP and QQ?
    You must show all your working and give your answers correct to 22 decimal places. [6 marks]

    (b)(i)(b)(ii)(c)(c)
    [Total 15 marks]
    Show solution & mark schemeHide solution & mark scheme

    Question 8 - Exam Solution

    Understanding the Question
    Given
    The curve y=x2+7x18y = x^2 + 7x - 18, and a blank pair of axes to sketch it on.
    The curve y=x23x28y = x^2 - 3x - 28, used in parts (b) and (c).
    The line y=52xy = 5 - 2x, which cuts that curve at PP and QQ.
    Find
    A sketch of y=x2+7x18y = x^2 + 7x - 18 carrying the values where it meets each axis. The derivative of y=x23x28y = x^2 - 3x - 28, and the coordinates of its turning point. The coordinates of PP and QQ, each correct to 22 decimal places.
    Plan the Solution
    • A sketch needs three things: which way up the curve is, where it cuts each axis, and roughly where its lowest point sits.
    • The x2x^2 term is positive, so the curve is U shaped, and it meets the xx-axis where the right-hand side factorises to zero.
    • Putting x=0x = 0 in gives the yy-axis value in one line, because it leaves only the constant term.
    • The lowest point of a U shaped quadratic sits halfway between its two xx-axis values.
    • A turning point is where the gradient is zero, so differentiate first and then solve.
    • Two graphs meet where their yy-values agree, so set the two right-hand sides equal and collect every term on one side.
    • The quadratic that comes out has no factors, so the formula is the way through, and the y-values then come from the simpler of the two equations.
    Worked Solution [15 marks]
    Rule - Sketching a quadratic, and where two graphs meet: factorise for the xx-axis values, put x=0x = 0 for the yy-axis value, solve dydx=0\dfrac{dy}{dx} = 0 for a turning point, and set the two expressions for yy equal where two graphs cross.
    (a) Factorise the right-hand side
    x2+7x18=(x+9)(x2)x^2 + 7x - 18 = (x + 9)(x - 2)
    yxO−92−18
    (Reason: Two numbers that multiply to 18-18 and add to 77 are 99 and 2-2.)
    (a) The values where the graph meets the xx-axis
    (x+9)(x2)=0(x + 9)(x - 2) = 0
    x=9orx=2x = -9 \quad \text{or} \quad x = 2
    (Reason: The graph meets the xx-axis where y=0y = 0, and a product is zero only when one of its brackets is zero.)
    (a) The value where the graph meets the yy-axis
    y=02+7(0)18=18y = 0^2 + 7(0) - 18 = -18
    (Reason: Every point on the yy-axis has x=0x = 0, so only the constant term survives.)
    (a) The lowest point, so the curve can be placed
    x=9+22=3.5x = \dfrac{-9 + 2}{2} = -3.5
    y=(3.5)2+7(3.5)18=30.25y = (-3.5)^2 + 7(-3.5) - 18 = -30.25
    (Reason: A U shaped quadratic is symmetrical, so its lowest point is halfway between the two xx-axis values. Both coordinates are negative, which puts the lowest point in the third quadrant.)
    (a) Draw the curve
    y=x2+7x18y = x^2 + 7x - 18
    (Reason: The coefficient of x2x^2 is positive, so the curve is U shaped. Mark 9-9 and 22 on the xx-axis and 18-18 on the yy-axis, write those three values beside the marks, and draw one smooth curve through them.)
    (b)(i) Differentiate term by term
    y=x23x28y = x^2 - 3x - 28
    dydx=2x3\dfrac{dy}{dx} = 2x - 3
    (Reason: Bring each power down in front and drop it by one: x2x^2 gives 2x2x, 3x-3x gives 3-3, and a constant has no gradient of its own.)
    (b)(ii) The gradient is zero at a turning point
    2x3=02x - 3 = 0
    x=1.5x = 1.5
    (Reason: The curve is level for an instant at its turning point, so set the derivative from part (b)(i) equal to zero and solve.)
    (b)(ii) The yy-coordinate of the turning point
    y=1.523(1.5)28y = 1.5^2 - 3(1.5) - 28
    y=2.254.528=30.25y = 2.25 - 4.5 - 28 = -30.25
    (Reason: The turning point lies on the curve, so put the xx-value back into the equation of the curve rather than into the derivative.)
    (c) The line and the curve share a yy-value where they cross
    x23x28=52xx^2 - 3x - 28 = 5 - 2x
    (Reason: At PP and at QQ the point lies on both graphs, so the two expressions for yy must be equal there.)
    (c) Collect every term on one side
    x23x285+2x=0x^2 - 3x - 28 - 5 + 2x = 0
    x2x33=0x^2 - x - 33 = 0
    (Reason: Take 55 from both sides and add 2x2x to both sides. The 3x-3x and the 2x2x leave x-x, and 285-28 - 5 leaves 33-33.)
    (c) No factors, so use the formula
    x=(1)±(1)24(1)(33)2(1)x = \dfrac{-(-1) \pm \sqrt{(-1)^2 - 4(1)(-33)}}{2(1)}
    x=1±1332x = \dfrac{1 \pm \sqrt{133}}{2}
    (Reason: Here a=1a = 1, b=1b = -1 and c=33c = -33. Under the root, 1+132=1331 + 132 = 133, which is not a square number, so the answers will not be exact.)
    (c) The two xx-values
    x=1+11.53252=6.2662x = \dfrac{1 + 11.5325\ldots}{2} = 6.2662\ldots
    x=111.53252=5.2662x = \dfrac{1 - 11.5325\ldots}{2} = -5.2662\ldots
    (Reason: Keep the whole calculator display at this stage. Rounding here would move the second decimal place of the yy-values.)
    (c) The matching yy-values
    y=52(6.2662)=7.5325y = 5 - 2(6.2662\ldots) = -7.5325\ldots
    y=52(5.2662)=15.5325y = 5 - 2(-5.2662\ldots) = 15.5325\ldots
    (Reason: Use the line, not the curve: y=52xy = 5 - 2x is the shorter calculation and gives the same point. Watch the second one, where subtracting a negative adds.)
    (c) Round to 22 decimal places
    (5.27, 15.53)(-5.27,\ 15.53)
    (6.27, 7.53)(6.27,\ -7.53)
    (Reason: The third decimal place is 66 in both xx-values, so each of those rounds up, and 22 in both yy-values, so each of those stays as it is.)
    (a) a U shaped curve through (9, 0)(-9,\ 0), (2, 0)(2,\ 0) and (0, 18)(0,\ -18)(b)(i) dydx=2x3\dfrac{dy}{dx} = 2x - 3(b)(ii) (1.5, 30.25)(1.5,\ -30.25)(c) (5.27, 15.53)(-5.27,\ 15.53) and (6.27, 7.53)(6.27,\ -7.53)
    Verification
    Check 1: Expand the brackets again and see the original expression come back. (x+9)(x2)=x22x+9x18=x2+7x18(x + 9)(x - 2) = x^2 - 2x + 9x - 18 = x^2 + 7x - 18
    Check 2: Put both xx-axis values back into y=x2+7x18y = x^2 + 7x - 18; each must give zero. 816318=081 - 63 - 18 = 0 and 4+1418=04 + 14 - 18 = 0.
    Check 3: Find the turning point of y=x23x28y = x^2 - 3x - 28 without differentiating, by completing the square. Completing the square gives (x1.5)230.25(x - 1.5)^2 - 30.25, which is smallest when the bracket is zero, so the turning point is (1.5, 30.25)(1.5,\ -30.25). Part (a)'s curve reaches the same depth, since 1812.25=30.25-18 - 12.25 = -30.25.
    Check 4: Both points must sit on the line, so put the rounded xx-values into y=52xy = 5 - 2x. 52(5.27)=15.545 - 2(-5.27) = 15.54 and 52(6.27)=7.545 - 2(6.27) = -7.54, each within 0.010.01 of the rounded yy-values, which is why the mark scheme accepts either figure.
    Check 5: The two solutions of x2x33=0x^2 - x - 33 = 0 must add to 11, because the coefficient of xx is 1-1. 5.2662+6.2662=1-5.2662\ldots + 6.2662\ldots = 1, and the two values sit either side of 0.50.5, the line of symmetry of that quadratic.
    Mark Scheme Breakdown
    StepMarkDescriptionGot it?
    (a) The sketchNoteThe Answer column gives correct sketch with roots indicated at x=9x = -9 and x=2x = 2 and yy intercept = 18-18, minimum should be in 3rd quadrant, and the Marks column gives 44 for it.
    (a) The shape of the curveB1For a U shaped parabola.
    (a) The two values on the xx-axisB2For roots at 9-9 and 22 on diagram.
    (a) The factorisation insteadM1Or for (x+9)(x2)  [=0](x + 9)(x - 2) \; [= 0].
    (a) The value on the yy-axisB1For yy – intercept at 18-18 on diagram.
    (a) The cap on the sketchNoteMaximum 3 marks if sketch not fully correct.
    (b)(i) The derivativeNoteThe Answer column gives 2x32x - 3, and the Marks column gives 22 for it.
    (b)(i) One term differentiated correctlyB1For 2x+k2x + k or kx[p]3kx^{[p]} - 3.
    (b)(ii) The turning pointNoteThe Answer column gives (1.5, 30.25)(1.5,\ -30.25) oe, and the Marks column gives 33 for it.
    (b)(ii) The xx-coordinate aloneB2For x=1.5x = 1.5.
    (b)(ii) The derivative set to zero, or the completed squareM1Or for their (b)(i)=0\text{their (b)(i)} = 0, or for (x1.5)2(x - 1.5)^2.
    (c) The rearranged quadraticB1For x2x33  [=0]x^2 - x - 33 \; [= 0] seen.
    (c) How the formula row follows throughNoteFT their quadratic dep on no factors.
    (c) The quadratic formula with the right values in itB2FTFor []1±([]1)24(1)(33)2×1\dfrac{[--]1 \pm \sqrt{([-]1)^2 - 4(1)(-33)}}{2 \times 1} oe.
    (c) The discriminant under the rootB1For ([]1)24(1)(33)\sqrt{([-]1)^2 - 4(1)(-33)} or better.
    (c) One branch of the formulaB1Or for []1+q2(1)\dfrac{[--]1 + \sqrt{q}}{2(1)} oe or []1q2(1)\dfrac{[--]1 - \sqrt{q}}{2(1)} oe.
    (c) The two xx-valuesB2For 5.27-5.27 or 5.267-5.267 to 5.266-5.266 and 6.276.27 or 6.2666.266 to 6.2676.267.
    (c) One of the two xx-valuesB1For each.
    (c) The special case for two swapped signsSC1If 0 scored, for 6.27-6.27 and 5.275.27.
    (c) The two pointsB1For (5.27, 15.53 or 15.54)(-5.27,\ 15.53 \text{ or } 15.54) and (6.27, 7.53 or 7.54)(6.27,\ -7.53 \text{ or } -7.54).

    Full marks: 15/15

    Question 9, Calculator allowed

    f(x)=4x+1g(x)=62xh(x)=3x2\mathrm{f}(x) = 4x + 1 \qquad \mathrm{g}(x) = 6 - 2x \qquad \mathrm{h}(x) = 3^{x-2}

    (a) Work out the value of each of the following.
    (i) f(3)\mathrm{f}(3) [1 mark]

    (ii) gf(3)\mathrm{gf}(3) [1 mark]

    (b) What is g1(x)\mathrm{g}^{-1}(x)? [2 marks]

    (c) When f(x)=g(2x7)\mathrm{f}(x) = \mathrm{g}(2x - 7), what is the value of xx? [4 marks]

    (d) What is the value of hh(2)\mathrm{hh}(2)? [2 marks]

    (e) For which value of xx is h1(x)=10\mathrm{h}^{-1}(x) = 10? [2 marks]

    (a)(i)(a)(ii)(b) g⁻¹(x) =(c) x =(d)(e) x =
    [Total 12 marks]
    Show solution & mark schemeHide solution & mark scheme

    Question 9 - Exam Solution

    Understanding the Question
    Given
    f(x)=4x+1\mathrm{f}(x) = 4x + 1
    g(x)=62x\mathrm{g}(x) = 6 - 2x
    h(x)=3x2\mathrm{h}(x) = 3^{x-2}
    Two linear functions and one function with the variable in the index.
    Find
    (a)(i) f(3)\mathrm{f}(3) and (ii) gf(3)\mathrm{gf}(3) (b) the inverse g1(x)\mathrm{g}^{-1}(x) (c) xx when f(x)=g(2x7)\mathrm{f}(x) = \mathrm{g}(2x - 7) (d) hh(2)\mathrm{hh}(2) (e) xx when h1(x)=10\mathrm{h}^{-1}(x) = 10
    Plan the Solution
    • To evaluate a function at a number, replace every xx in its formula by that number.
    • In gf(3)\mathrm{gf}(3) the function written nearest the number acts first, so work out f(3)\mathrm{f}(3) and feed the result into g\mathrm{g}.
    • For the inverse, write y=g(x)y = \mathrm{g}(x), make xx the subject, then rename the letters.
    • For (c), put 2x72x - 7 into g\mathrm{g} first, then solve the linear equation that is left.
    • For (d), work outwards: h(2)\mathrm{h}(2) first, then h\mathrm{h} of that answer.
    • For (e), an inverse undoes its function, so h1(x)=10\mathrm{h}^{-1}(x) = 10 is the same statement as x=h(10)x = \mathrm{h}(10).
    Worked Solution [12 marks]
    Rule - Composite and inverse functions: gf(x)\mathrm{gf}(x) means apply f\mathrm{f} first and then g\mathrm{g}; and an inverse reverses a function, so g1(y)=x\mathrm{g}^{-1}(y) = x exactly when g(x)=y\mathrm{g}(x) = y.
    Step 1: (a)(i) Put 33 in place of xx in f\mathrm{f}
    f(3)=4×3+1\mathrm{f}(3) = 4 \times 3 + 1
    4×3+1=12+1=134 \times 3 + 1 = 12 + 1 = 13
    (Reason: the formula 4x+14x + 1 is a rule for what to do to its input, so the 33 is multiplied by 44 before the 11 is added)
    Step 2: (a)(ii) Apply f\mathrm{f} first, then g\mathrm{g}
    gf(3)=g(13)\mathrm{gf}(3) = \mathrm{g}(13)
    g(13)=62×13\mathrm{g}(13) = 6 - 2 \times 13
    62×13=626=206 - 2 \times 13 = 6 - 26 = -20
    (Reason: the function written nearest the number acts first, so the 1313 from part (i) becomes the input of g\mathrm{g})
    Step 3: (b) Make xx the subject of y=62xy = 6 - 2x
    y=62xy = 6 - 2x
    2x=6y2x = 6 - y
    x=6y2x = \dfrac{6 - y}{2}
    g1(x)=6x2\mathrm{g}^{-1}(x) = \dfrac{6 - x}{2}
    (Reason: the inverse sends an output of g\mathrm{g} back to the input it came from, so the working is that rearrangement; the letters are renamed at the end because an inverse is written as a function of xx)
    Step 4: (c) Feed 2x72x - 7 into g\mathrm{g}
    g(2x7)=62(2x7)\mathrm{g}(2x - 7) = 6 - 2(2x - 7)
    62(2x7)=64x+146 - 2(2x - 7) = 6 - 4x + 14
    64x+14=204x6 - 4x + 14 = 20 - 4x
    (Reason: both terms inside the bracket are multiplied by 2-2, and a negative multiplied by a negative is positive, so the constant term grows rather than shrinks)
    Step 5: (c) Collect the terms and solve
    4x+1=204x4x + 1 = 20 - 4x
    4x+4x=2014x + 4x = 20 - 1
    8x=198x = 19
    x=198=2.375x = \dfrac{19}{8} = 2.375
    (Reason: the xx terms go on one side and the numbers on the other, which leaves a single division by 88)
    Step 6: (d) Work outwards for hh(2)\mathrm{hh}(2)
    h(2)=322=30=1\mathrm{h}(2) = 3^{2-2} = 3^{0} = 1
    hh(2)=h(1)\mathrm{hh}(2) = \mathrm{h}(1)
    312=31=133^{1-2} = 3^{-1} = \dfrac{1}{3}
    (Reason: the inner h\mathrm{h} acts first and gives 11, and that 11 is then the input of the outer h\mathrm{h})
    Step 7: (e) Turn the inverse statement round
    h1(x)=10\mathrm{h}^{-1}(x) = 10
    x=h(10)=3102x = \mathrm{h}(10) = 3^{10-2}
    3102=38=65613^{10-2} = 3^{8} = 6561
    (Reason: an inverse undoes its function, so saying that h1\mathrm{h}^{-1} sends xx to 1010 is the same as saying that h\mathrm{h} sends 1010 to xx)
    (a)(i) 1313(a)(ii) 20-20(b) g1(x)=6x2\mathrm{g}^{-1}(x) = \dfrac{6 - x}{2}(c) x=2.375x = 2.375(d) 13\dfrac{1}{3}(e) x=6561x = 6561
    Verification
    Check 1 - part (a)(ii): Compose the two functions into one formula first, gf(x)=62(4x+1)=48x\mathrm{gf}(x) = 6 - 2(4x + 1) = 4 - 8x, then put x=3x = 3 into that instead. 48×3=424=204 - 8 \times 3 = 4 - 24 = -20
    Check 2 - part (b): g(5)=610=4\mathrm{g}(5) = 6 - 10 = -4, so the inverse must send 4-4 back to 55. 6(4)2=102=5\dfrac{6 - (-4)}{2} = \dfrac{10}{2} = 5
    Check 3 - part (c): Put x=2.375x = 2.375 into each side of f(x)=g(2x7)\mathrm{f}(x) = \mathrm{g}(2x - 7) separately. The bracket gives 2×2.3757=2.252 \times 2.375 - 7 = -2.25. 4×2.375+1=10.54 \times 2.375 + 1 = 10.5 and 62×(2.25)=10.56 - 2 \times (-2.25) = 10.5
    Check 4 - part (d): A negative index is a reciprocal, not a negative number, so multiplying the answer by the base must give 11. 13×3=1\dfrac{1}{3} \times 3 = 1
    Check 5 - part (e): Divide 65616561 by 33 over and over: it takes 88 divisions to reach 11. 6561=386561 = 3^{8}, so the index x2x - 2 is 88 and x=10x = 10
    Mark Scheme Breakdown
    StepMarkDescriptionGot it?
    (a)(i) The value of f(3)\mathrm{f}(3)NoteThe Answer column gives 1313, and the Marks column gives 11 for it.
    (a)(ii) The value of gf(3)\mathrm{gf}(3)NoteThe Answer column gives 20-20, and the Marks column gives 11 for it.
    (a)(ii) The instruction printed in the Partial Marks columnNoteFT 62(their (a)(i))6 - 2(\textit{their} \text{ (a)(i)}).
    (b) The expression for g1(x)\mathrm{g}^{-1}(x)NoteThe Answer column gives 6x2\dfrac{6 - x}{2} oe final answer, and the Marks column gives 22 for it.
    (b) The first step of the rearrangementM1For the correct first step: x=62yx = 6 - 2y, y6=2xy - 6 = -2x, y2=3x\dfrac{y}{2} = 3 - x.
    (c) The value of xxNoteThe Answer column gives 2.3752.375 oe, and the Marks column gives 44 for it.
    (c) Substituting 2x72x - 7 into g\mathrm{g}B1For 62(2x7)6 - 2(2x - 7) oe.
    (c) Expanding the bracketB1For 4x+1=64x+144x + 1 = 6 - 4x + 14.
    (c) Rearranging to a single term in xM1For 8x=198x = 19 FT their linear equation rearranged correctly from ax+b=cx+dax + b = cx + d to form ex=fex = f.
    (d) The value of hh(2)\mathrm{hh}(2)NoteThe Answer column gives 13\dfrac{1}{3} or 0.3330.333\ldots, and the Marks column gives 22 for it.
    (d) Reaching the inner value, or writing the whole index expressionM1For h(1)\mathrm{h}(1) or 3(3x22)3^{(3^{x-2} - 2)} or 3(3222)3^{(3^{2-2} - 2)}, or better.
    (e) The value of xxNoteThe Answer column gives 65616561, and the Marks column gives 22 for it.
    (e) Turning the inverse statement roundM1For 31023^{10-2} or x=h(10)x = \mathrm{h}(10).

    Full marks: 12/12

    Keep revising

    That is the whole paper. Read what the IGCSE is and how it is graded, or compare Edexcel 4MA1 with Cambridge 0580 if you are still choosing a board. Check the IGCSE grade boundaries to set your target, and if the exam is close, the four-week IGCSE Maths revision plan sets out what to do week by week.

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