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Edexcel IGCSE 4MA1/2H, Wednesday 4 June 2025: Worked Solutions, Questions 20 to 26

Sir Faraz Hassan

Sir Faraz Hassan

31 Aug 2026

Table of Contents
    Edexcel International GCSE Mathematics A (4MA1)4MA1/2H - Higher Tier - Wednesday 4 June 2025100 marks  ·  2 hours  ·  Calculator allowed
    Back to questions 11 to 19

    This is the rest of the paper. Questions 1 to 19, the paper's overview and the frequently asked questions are on the first two pages.

    Original worked solutions for Edexcel International GCSE Mathematics A, Paper 4MA1/2H (Higher Tier), June 2025 series, sat Wednesday 4 June 2025 –100 marks, 2 hours, calculator allowed. The questions have been reworded; all numerical values match the original paper. The official question paper and mark scheme are published by Pearson Edexcel. This resource reproduces neither the exam paper nor the official mark scheme.
    Both are PDF files hosted by Pearson: 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 accuracy mark (A1) is earned. The questions follow the same order as the original paper and carry the same marks.

    Download printable PDF

    All 26 questions with a full worked solution and mark scheme - free PDF

    Worked solutions, questions 20 to 26 of 26

    Question 20, Calculator allowed

    120120 members of a sports club were asked whether they play cricket (C)(C) or padel (P)(P) or tennis (T)(T)

    CPT

    Of these members

    4343 play cricket
    1212 play cricket and padel and tennis
    1818 play cricket and padel
    2727 play cricket and tennis
    3232 play padel and tennis
    2929 do not play cricket or padel or tennis

    The number of these members who play only padel is equal to the number of these members who play only tennis.

    (a) Complete the Venn diagram to show this information.

    [3 marks]

    (b) Find n(TC)\text{n}(T' \cap C) [1 mark]

    One of the members who plays cricket is chosen at random.

    (c) Calculate the probability that this member also plays padel. [2 marks]

    (b)(c)
    [Total 6 marks]
    Show solution & mark schemeHide solution & mark scheme

    Question 20 - Exam Solution

    Understanding the Question
    Given
    A sports club with 120120 members, each asked whether they play cricket CC, padel PP or tennis TT.
    n(C)=43\text{n}(C) = 43, n(CP)=18\text{n}(C \cap P) = 18, n(CT)=27\text{n}(C \cap T) = 27, n(PT)=32\text{n}(P \cap T) = 32, n(CPT)=12\text{n}(C \cap P \cap T) = 12.
    2929 members play none of the three, and the number who play only padel equals the number who play only tennis.
    Find
    (a) The number in each of the eight regions of the Venn diagram. (b) n(TC)\text{n}(T' \cap C). (c) The probability that a member chosen at random from the cricket players also plays padel.
    Plan the Solution
    • Start in the middle, where all three circles overlap, because that number is given outright.
    • Take the middle away from each pair total to get the three regions where exactly two sports are played.
    • Subtract the three known cricket regions from 4343 to leave cricket only.
    • Everything inside the circles comes to 12029120 - 29, so the two equal regions left over can be found and halved.
    • Read part (b) off the finished diagram, then write part (c) as a fraction of the 4343 cricket players and not of all 120120 members.
    Worked Solution [6 marks]
    Rule - Fill a Venn diagram from the centre outwards. Every overlap total already contains the region in the middle, so subtract it: n(CP)n(CPT)\text{n}(C \cap P) - \text{n}(C \cap P \cap T) is the number in both CC and PP but not in TT. When the diagram is complete, all eight regions must add up to 120120.
    Step 1: Write in the middle region
    n(CPT)=12\text{n}(C \cap P \cap T) = 12
    CPT106141512201429
    (Reason: The question gives the number who play all three sports outright, and every other overlap total contains it, so nothing else can be worked out until it is in place.)
    Step 2: Take the middle out of each pair total
    1812=618 - 12 = 6
    2712=1527 - 12 = 15
    3212=2032 - 12 = 20
    (Reason: The 1818 who play cricket and padel includes the 1212 who play all three, so only 66 play cricket and padel but not tennis. The same subtraction leaves 1515 for cricket and tennis only and 2020 for padel and tennis only.)
    Step 3: Finish the cricket circle
    43(6+12+15)=4333=1043 - (6 + 12 + 15) = 43 - 33 = 10
    (Reason: The cricket circle holds 4343 members altogether. Three of its four regions are now known, so taking those off leaves the members who play cricket and nothing else.)
    Step 4: Use the total to split the last two regions
    12029=91120 - 29 = 91
    91(10+6+15+12+20)=2891 - (10 + 6 + 15 + 12 + 20) = 28
    282=14\dfrac{28}{2} = 14
    (Reason: 2929 members play none of the three sports, so 9191 are somewhere inside the circles. Taking away the five regions already filled leaves 2828 to share between padel only and tennis only, and the question says those two are equal, so each of them is 1414.)
    Step 5: Read n(TC)\text{n}(T' \cap C) off the diagram
    n(TC)=10+6=16\text{n}(T' \cap C) = 10 + 6 = 16
    (Reason: TT' is everything outside the tennis circle, so TCT' \cap C is the part of the cricket circle that the tennis circle does not reach. That is cricket only together with cricket and padel only, 10+610 + 6.)
    Step 6: Write part (c) as a fraction of the cricket players
    6+12=186 + 12 = 18
    1843\dfrac{18}{43}
    (Reason: The member is picked from the cricket players only, so the denominator is 4343 and not 120120. Of those 4343, the ones who also play padel are the 66 in cricket and padel only plus the 1212 who play all three.)
    (a) CC only 1010, PP only 1414, TT only 1414, all three 1212 CC and PP only 66, CC and TT only 1515, PP and TT only 2020, none 2929(b) 1616(c) 1843\dfrac{18}{43}
    Verification
    Check 1: Add every region on the finished diagram: 10+6+14+15+12+20+14+2910 + 6 + 14 + 15 + 12 + 20 + 14 + 29. The eight regions come to 120120, the number of members surveyed, so nobody has been left out or counted twice.
    Check 2: Count each circle off the finished diagram - n(P)=6+14+12+20\text{n}(P) = 6 + 14 + 12 + 20 and n(T)=15+12+20+14\text{n}(T) = 15 + 12 + 20 + 14 - then put the three circle totals through the inclusion and exclusion rule. 43+52+61182732+12=9143 + 52 + 61 - 18 - 27 - 32 + 12 = 91, which is exactly 12029120 - 29, so the circle totals agree with the overlap figures the question gives.
    Check 3: The padel players inside the cricket circle should come back to the 1818 the question states for cricket and padel, and the probability should sit a little under a half. 6+12=186 + 12 = 18, and 1843=0.4186\dfrac{18}{43} = 0.4186 to four decimal places, which is just below 0.50.5 as expected because 1818 is a little under half of 4343.
    Mark Scheme Breakdown
    StepMarkDescriptionGot it?
    (a) The completed Venn diagramB3For all numbers in correct regions: 1010, 66, 1414, 1515, 1212, 2020, 1414, 2929. B2 for 55, 66 or 77 correct numbers. B1 for 33 or 44 correct numbers.
    (b) n(TC)\text{n}(T' \cap C)B11616. Follow through for their aa plus their bb. Do not follow through if there are no values for aa and bb.
    (c) A correct probability methodM1For n43\dfrac{n}{43} where n<43n < 43 or 18m\dfrac{18}{m} where m>18m > 18 or follow through their b+cp\dfrac{b + c}{p} where p>b+cp > b + c or follow through their qa+b+c+d\dfrac{q}{a + b + c + d} where q<a+b+c+dq < a + b + c + d. Do not follow through if there are no values for aa, bb, cc and dd.
    (c) The probabilityA11843\dfrac{18}{43} or equivalent, for example 0.41(860)0.41(860\ldots) or 41(.860)%41(.860\ldots)\% truncated or rounded, or follow through their b+ca+b+c+d\dfrac{b + c}{a + b + c + d} as a fraction or a decimal or a percentage.
    NoteNoteThe printed scheme shades four regions of the cricket circle and names them on its own diagrams: aa is CC only, bb is CC and PP only, cc is the region all three share and dd is CC and TT only. So a+b+c+da + b + c + d is the whole of CC and b+cb + c is CPC \cap P.

    Full marks: 6/6

    Question 21, Calculator allowed

    The diagram shows a cuboid.

    2x cm3x cmy cmDiagram NOTaccurately drawn

    The edges of the cuboid are 3x3x cm, 2x2x cm and yy cm
    This cuboid has a volume of 10141014 cm³
    Its total surface area is AA cm²

    Show that A=12x2+1690xA = 12x^2 + \dfrac{1690}{x}
    You must show every stage of your working. [3 marks]

    [Total 3 marks]
    Show solution & mark schemeHide solution & mark scheme

    Question 21 - Exam Solution

    Understanding the Question
    Given
    A cuboid with edges 3x3x cm, 2x2x cm and yy cm
    The volume is 10141014 cm³
    The total surface area is AA cm²
    Find
    Show that A=12x2+1690xA = 12x^2 + \dfrac{1690}{x}, so the surface area is written in terms of xx alone
    Plan the Solution
    • Use the volume to link xx and yy: multiply the three edges together and set the product equal to 10141014.
    • Rearrange that equation to make yy the subject.
    • Add the three pairs of faces to get the surface area in terms of xx and yy.
    • Replace yy by its expression in xx, so that only xx is left.
    Worked Solution [3 marks]
    Rule - Cuboid: a cuboid with edges aa, bb and cc has volume abcabc and total surface area 2ab+2bc+2ca2ab + 2bc + 2ca, because the six faces come in three matching pairs.
    Step 1: write an equation for the volume
    3x×2x×y=10143x \times 2x \times y = 1014
    6x2y=10146x^2y = 1014
    x2y=169x^2y = 169
    (Reason: (Reason: the volume of a cuboid is the product of its three edges, and 3x×2x=6x23x \times 2x = 6x^2. Dividing both sides by 66 gives the tidier form, because 10146=169\dfrac{1014}{6} = 169.))
    Step 2: make yy the subject
    y=169x2y = \dfrac{169}{x^2}
    (Reason: (Reason: dividing both sides of x2y=169x^2y = 169 by x2x^2 leaves yy on its own, so from here every yy can be written in terms of xx.))
    Step 3: write the surface area in terms of xx and yy
    A=2(3x×2x)+2(3x×y)+2(2x×y)A = 2(3x \times 2x) + 2(3x \times y) + 2(2x \times y)
    A=12x2+6xy+4xyA = 12x^2 + 6xy + 4xy
    A=12x2+10xyA = 12x^2 + 10xy
    (Reason: (Reason: the faces come in three pairs. The top and bottom are each 3x3x by 2x2x, the front and back are each 3x3x by yy, and the two ends are each 2x2x by yy. The two xyxy terms then collect into one.))
    Step 4: replace yy and simplify
    A=12x2+10x×169x2A = 12x^2 + 10x \times \dfrac{169}{x^2}
    10x×169x2=10×169x=1690x10x \times \dfrac{169}{x^2} = \dfrac{10 \times 169}{x} = \dfrac{1690}{x}
    A=12x2+1690xA = 12x^2 + \dfrac{1690}{x}
    (Reason: (Reason: yy has been replaced by 169x2\dfrac{169}{x^2}. One factor of xx cancels from the top and the bottom, which turns xx2\dfrac{x}{x^2} into 1x\dfrac{1}{x}, and that is the expression the question asks for.))
    Shown: A=12x2+1690xA = 12x^2 + \dfrac{1690}{x}
    Verification
    Check 1: Take x=1x = 1. The volume equation gives y=16912=169y = \dfrac{169}{1^2} = 169, so the cuboid measures 33 cm by 22 cm by 169169 cm. Its volume is 3×2×169=10143 \times 2 \times 169 = 1014 cm³, and adding the three pairs of faces gives 2×6+2×507+2×338=17022 \times 6 + 2 \times 507 + 2 \times 338 = 1702 cm². 12×12+16901=170212 \times 1^2 + \dfrac{1690}{1} = 1702, the same total
    Check 2: Take x=13x = 13, a value that makes the third edge short. Then y=169132=1y = \dfrac{169}{13^2} = 1, so the cuboid measures 3939 cm by 2626 cm by 11 cm. Its volume is 39×26×1=101439 \times 26 \times 1 = 1014 cm³, and adding the three pairs of faces gives 2×1014+2×39+2×26=21582 \times 1014 + 2 \times 39 + 2 \times 26 = 2158 cm². 12×132+169013=215812 \times 13^2 + \dfrac{1690}{13} = 2158, the same total again
    Check 3: Read the printed expression backwards. Matching 12x2+10xy12x^2 + 10xy with 12x2+1690x12x^2 + \dfrac{1690}{x} needs 10xy=1690x10xy = \dfrac{1690}{x}, and multiplying both sides by xx then dividing by 1010 gives x2y=169010x^2y = \dfrac{1690}{10}. x2y=169x^2y = 169, which is exactly the volume equation Step 1 produced, so the two ends of the working meet
    Mark Scheme Breakdown
    StepMarkDescriptionGot it?
    Form an equation for the volume in terms of xx and yyM13x×2x×y=10143x \times 2x \times y = 1014 oe or 6x2y=10146x^2y = 1014 oe or x2y=169x^2y = 169 oe. For an equation for volume in terms of xx and yy.
    Write a correct expression for the total surface areaM1 indep2×3x×y+2×2x×y+2×3x×2x2 \times 3x \times y + 2 \times 2x \times y + 2 \times 3x \times 2x oe or 2×(3xy+2xy+6x2)2 \times (3xy + 2xy + 6x^2) oe or 6xy+4xy+12x26xy + 4xy + 12x^2 oe or 10xy+12x210xy + 12x^2 oe. Independent of the first mark. NB the surface area expression may not be seen explicitly in terms of yy, eg 2×3x×169x2+2×2x×169x2+2×3x×2x2 \times 3x \times \dfrac{169}{x^2} + 2 \times 2x \times \dfrac{169}{x^2} + 2 \times 3x \times 2x oe. It may be fully substituted using y=169x2y = \dfrac{169}{x^2} oe.
    Complete the show thatA1 dep on M2Using y=10146x2y = \dfrac{1014}{6x^2} (=169x2)\left(= \dfrac{169}{x^2}\right) in the formula for the surface area to obtain a correct expression, eg (SA =) 2×5x×169x2+2×6x2=12x2+1690x2 \times 5x \times \dfrac{169}{x^2} + 2 \times 6x^2 = 12x^2 + \dfrac{1690}{x}, or equating their surface area equations, eg 10xy+12x2=12x2+1690x10xy + 12x^2 = 12x^2 + \dfrac{1690}{x} leading to x2y=169x^2y = 169 oe. Dependent on both method marks. For completing the show that by clearly showing the stages that lead to the given expression for the surface area.
    Working requiredNoteWorking required. Total 3 marks.

    Full marks: 3/3

    Question 22, Calculator allowed

    Rectangle ABCDABCD has a square drawn inside it, as shown in the diagram.

    ABCDDiagram NOTaccurately drawn

    The part of the rectangle that lies outside the square is shaded.
    The total area of the shaded region is X cm2X \text{ cm}^{2}.

    AB=11.5 cmAB = 11.5 \text{ cm} correct to the nearest 0.5 cm0.5 \text{ cm}
    BC=9.2 cmBC = 9.2 \text{ cm} correct to 22 significant figures
    side of the square =4.1 cm= 4.1 \text{ cm} correct to 22 significant figures

    By considering bounds, work out the value of XX to a suitable degree of accuracy.
    You must show your working clearly. [4 marks]

    X =
    [Total 4 marks]
    Show solution & mark schemeHide solution & mark scheme

    Question 22 - Exam Solution

    Understanding the Question
    Given
    The length ABAB is 11.5 cm11.5 \text{ cm}, correct to the nearest 0.5 cm0.5 \text{ cm}
    The length BCBC is 9.2 cm9.2 \text{ cm}, correct to 22 significant figures
    The side of the square, ss, is 4.1 cm4.1 \text{ cm}, correct to 22 significant figures
    The shaded region is the rectangle with the square removed, so XX is AB×BCs2AB \times BC - s^{2}
    Find
    The value of XX to a suitable degree of accuracy: the most accurate value that every possible set of measurements agrees on
    Plan the Solution
    • Write the lower and upper bound of each of the three lengths. A bound sits half a rounding unit either side of the value given.
    • The shaded area is a difference, so it is largest when the rectangle is largest and the square is smallest, and smallest when the rectangle is smallest and the square is largest.
    • Work out the upper bound of XX and the lower bound of XX.
    • Round both bounds to the same accuracy, starting with the most accurate, and stop at the first degree of accuracy where they agree. That shared value is XX.
    Worked Solution [4 marks]
    Rule - Bounds of a difference: to make PQP - Q as large as possible, take the upper bound of PP with the lower bound of QQ. To make it as small as possible, take the lower bound of PP with the upper bound of QQ.
    Step 1: Write down the bounds of the three lengths
    0.52=0.25\dfrac{0.5}{2} = 0.25
    0.12=0.05\dfrac{0.1}{2} = 0.05
    11.25AB<11.7511.25 \leq AB < 11.75
    9.15BC<9.259.15 \leq BC < 9.25
    4.05s<4.154.05 \leq s < 4.15
    (Reason: ABAB is given to the nearest 0.5 cm0.5 \text{ cm}, so its bounds are 0.250.25 either side of 11.511.5. Giving 9.29.2 and 4.14.1 to 22 significant figures is rounding to the nearest 0.1 cm0.1 \text{ cm}, so those bounds are 0.050.05 either side.)
    Step 2: The upper bound of XX
    11.75×9.254.052=108.687516.4025=92.28511.75 \times 9.25 - 4.05^{2} = 108.6875 - 16.4025 = 92.285
    (Reason: The shaded area is as large as it can be when the rectangle is as large as it can be and the square taken out of it is as small as it can be, so this uses 11.7511.75, 9.259.25 and 4.054.05.)
    Step 3: The lower bound of XX
    11.25×9.154.152=102.937517.2225=85.71511.25 \times 9.15 - 4.15^{2} = 102.9375 - 17.2225 = 85.715
    (Reason: The shaded area is as small as it can be when the rectangle is as small as it can be and the square taken out of it is as large as it can be, so this uses 11.2511.25, 9.159.15 and 4.154.15.)
    Step 4: Round both bounds until they agree
    92.28592 (2 s.f.)92.285 \approx 92 \text{ (2 s.f.)}
    85.71586 (2 s.f.)85.715 \approx 86 \text{ (2 s.f.)}
    92.28590 (1 s.f.)92.285 \approx 90 \text{ (1 s.f.)}
    85.71590 (1 s.f.)85.715 \approx 90 \text{ (1 s.f.)}
    (Reason: To 22 significant figures the two bounds give 9292 and 8686, which are different, so that is more accuracy than the measurements support. To 11 significant figure both give 9090, so every value the shaded area could take rounds to the same number, and that number is the answer.)
    X=90X = 90 (to 11 significant figure)
    Verification
    Check 1 - round both bounds together: Round the upper bound and the lower bound to the same accuracy and compare them. To 22 significant figures they are 9292 and 8686. They disagree at 22 significant figures and agree at 11, which gives 9090.
    Check 2 - use the measurements as they are stated: Work out the shaded area from the stated lengths themselves: 11.5×9.24.1211.5 \times 9.2 - 4.1^{2}. 105.816.81=88.99105.8 - 16.81 = 88.99, which lies between the two bounds and also rounds to 9090.
    Check 3 - pair the bounds the other way round: Take the largest rectangle with the largest square, and the smallest rectangle with the smallest square: 11.75×9.254.152=91.46511.75 \times 9.25 - 4.15^{2} = 91.465 and 11.25×9.154.052=86.53511.25 \times 9.15 - 4.05^{2} = 86.535. Both sit inside 85.71585.715 to 92.28592.285, so the pairings used above really are the extreme ones.
    Mark Scheme Breakdown
    StepMarkDescriptionGot it?
    11.2511.25, 11.7511.75, 9.159.15, 9.259.25, 4.054.05, 4.154.15B1for a correct bound. Accept 11.749˙11.74\dot{9} or 11.74911.74\overline{9} for 11.7511.75, 9.249˙9.24\dot{9} or 9.2499.24\overline{9} for 9.259.25, 4.149˙4.14\dot{9} or 4.1494.14\overline{9} for 4.154.15
    11.75×9.254.052  (=92.285)11.75 \times 9.25 - 4.05^{2} \; (= 92.285)M1for a correct method to find the upper bound of XX, allow (11.5<AB11.75)×(9.2<BC9.25)((4.05s<4.1)2)(11.5 < AB \leq 11.75) \times (9.2 < BC \leq 9.25) - \left( (4.05 \leq s < 4.1)^{2} \right)
    11.25×9.154.152  (=85.715)11.25 \times 9.15 - 4.15^{2} \; (= 85.715)M1for a correct method to find the lower bound of XX, allow (11.25AB<11.5)×(9.15BC<9.2)((4.1<s4.15)2)(11.25 \leq AB < 11.5) \times (9.15 \leq BC < 9.2) - \left( (4.1 < s \leq 4.15)^{2} \right)
    Working requiredA1dep on M2. 9090, and both the upper bound and the lower bound correct using the correct values 11.2511.25, 11.7511.75, 9.159.15, 9.259.25, 4.054.05 and 4.154.15

    Full marks: 4/4

    Question 23, Calculator allowed

    4x24x1205x2180x2+5x10x2+60x=p\dfrac{\dfrac{4x^{2} - 4x - 120}{5x^{2} - 180}}{\dfrac{x^{2} + 5x}{10x^{2} + 60x}} = p where pp is an integer.

    Work out the value of pp
    Show clear algebraic working. [4 marks]

    p =
    [Total 4 marks]
    Show solution & mark schemeHide solution & mark scheme

    Question 23 - Exam Solution

    Understanding the Question
    Given
    4x24x1205x2180x2+5x10x2+60x=p\dfrac{\dfrac{4x^{2} - 4x - 120}{5x^{2} - 180}}{\dfrac{x^{2} + 5x}{10x^{2} + 60x}} = p
    pp is an integer, so every xx has to cancel out.
    Find
    The value of pp
    Plan the Solution
    • Factorise all four expressions fully, top and bottom of both fractions.
    • Dividing by a fraction is multiplying by its reciprocal, so turn the second fraction upside down.
    • Cancel every bracket that appears on the top and on the bottom, then work out the numbers that are left.
    Worked Solution [4 marks]
    Rule - Dividing algebraic fractions: factorise every part, turn the second fraction upside down, multiply, then cancel.
    Step 1: Factorise the first fraction
    4x24x120=4(x2x30)=4(x6)(x+5)4x^{2} - 4x - 120 = 4(x^{2} - x - 30) = 4(x - 6)(x + 5)
    5x2180=5(x236)=5(x6)(x+6)5x^{2} - 180 = 5(x^{2} - 36) = 5(x - 6)(x + 6)
    (Reason: (Reason: take the common number out first. Then x2x30x^{2} - x - 30 needs two numbers with product 30-30 and sum 1-1, which are 6-6 and 55, while x236x^{2} - 36 is the difference of two squares.))
    Step 2: Factorise the second fraction
    x2+5x=x(x+5)x^{2} + 5x = x(x + 5)
    10x2+60x=10x(x+6)10x^{2} + 60x = 10x(x + 6)
    (Reason: (Reason: both terms of each expression contain an xx, and the bottom one also has a factor of 1010, so 10x10x comes out. The marks here are for factorising fully, not part way.))
    Step 3: Turn the second fraction upside down and multiply
    4(x6)(x+5)5(x6)(x+6)×10x(x+6)x(x+5)\dfrac{4(x - 6)(x + 5)}{5(x - 6)(x + 6)} \times \dfrac{10x(x + 6)}{x(x + 5)}
    (Reason: (Reason: dividing by x(x+5)10x(x+6)\dfrac{x(x + 5)}{10x(x + 6)} is the same as multiplying by its reciprocal 10x(x+6)x(x+5)\dfrac{10x(x + 6)}{x(x + 5)}.))
    Step 4: Cancel every factor that appears top and bottom
    4(x6)(x+5)×10x(x+6)5(x6)(x+6)×x(x+5)\dfrac{4(x - 6)(x + 5) \times 10x(x + 6)}{5(x - 6)(x + 6) \times x(x + 5)}
    4×105=405=8\dfrac{4 \times 10}{5} = \dfrac{40}{5} = 8
    (Reason: (Reason: (x6)(x - 6), (x+5)(x + 5), (x+6)(x + 6) and xx each appear on the top and on the bottom, so all four cancel and only the numbers are left.))
    p=8p = 8
    Verification
    Check 1: Put x=1x = 1 into the original expression. The first fraction becomes 441205180=120175=2435\dfrac{4 - 4 - 120}{5 - 180} = \dfrac{-120}{-175} = \dfrac{24}{35} and the second becomes 1+510+60=670=335\dfrac{1 + 5}{10 + 60} = \dfrac{6}{70} = \dfrac{3}{35}, so divide the first by the second. 2435×353=8\dfrac{24}{35} \times \dfrac{35}{3} = 8
    Check 2: Try a second value, x=2x = 2. Now the first fraction is 16812020180=112160=710\dfrac{16 - 8 - 120}{20 - 180} = \dfrac{-112}{-160} = \dfrac{7}{10} and the second is 4+1040+120=14160=780\dfrac{4 + 10}{40 + 120} = \dfrac{14}{160} = \dfrac{7}{80}. This is a check only: the mark scheme says substituting values of xx is not an acceptable algebraic method for the marks. 710×807=8\dfrac{7}{10} \times \dfrac{80}{7} = 8
    Check 3: Multiply everything out instead of factorising. One fraction is left, 40x4+200x31440x27200x5x4+25x3180x2900x\dfrac{40x^{4} + 200x^{3} - 1\,440x^{2} - 7\,200x}{5x^{4} + 25x^{3} - 180x^{2} - 900x}, so each coefficient on the top should be 88 times the one underneath it. 8×5=408 \times 5 = 40, 8×25=2008 \times 25 = 200, 8×(180)=14408 \times (-180) = -1\,440, 8×(900)=72008 \times (-900) = -7\,200
    Mark Scheme Breakdown
    StepMarkDescriptionGot it?
    4(x6)(x+5)5(x6)(x+6)x(x+5)10x(x+6)\dfrac{\dfrac{4(x - 6)(x + 5)}{5(x - 6)(x + 6)}}{\dfrac{x(x + 5)}{10x(x + 6)}} (=p)(= p) or 4(x6)(x+5)5(x6)(x+6)×10x(x+6)x(x+5)\dfrac{4(x - 6)(x + 5)}{5(x - 6)(x + 6)} \times \dfrac{10x(x + 6)}{x(x + 5)} (=p)(= p)
    or 2 from 4(x6)(x+5)4(x - 6)(x + 5) or 5(x6)(x+6)5(x - 6)(x + 6) or x(x+5)x(x + 5) or 10x(x+6)10x(x + 6)
    M1for factorising 2 or 3 of the quadratics fully - could be implied by 2 factors cancelled correctly. NB factors must be in the form (ax+b)(ax + b). NB Substitution of values of xx into the given equation is not an acceptable algebraic method
    4(x6)(x+5)5(x6)(x+6)x(x+5)10x(x+6)\dfrac{\dfrac{4(x - 6)(x + 5)}{5(x - 6)(x + 6)}}{\dfrac{x(x + 5)}{10x(x + 6)}} (=p)(= p) or 4(x6)(x+5)5(x6)(x+6)×10x(x+6)x(x+5)\dfrac{4(x - 6)(x + 5)}{5(x - 6)(x + 6)} \times \dfrac{10x(x + 6)}{x(x + 5)} (=p)(= p)
    or 4(x6)(x+5)4(x - 6)(x + 5) and 5(x6)(x+6)5(x - 6)(x + 6) and x(x+5)x(x + 5) and 10x(x+6)10x(x + 6)
    M1for factorising all of the quadratics fully - could be implied by 2 factors cancelled correctly. NB factors must be in the form (ax+b)(ax + b)
    4x24x1205x2180×10x2+60xx2+5x\dfrac{4x^{2} - 4x - 120}{5x^{2} - 180} \times \dfrac{10x^{2} + 60x}{x^{2} + 5x} (=p)(= p)M1for inverting the 2nd fraction (this mark can be awarded at any time and may be awarded with incorrect factorisation if meaning is clear)
    Working requiredA188 oe dep on M3
    ALT 40x4+200x31440x27200x5x4+25x3180x2900x\dfrac{40x^{4} + 200x^{3} - 1\,440x^{2} - 7\,200x}{5x^{4} + 25x^{3} - 180x^{2} - 900x}Notethe printed scheme carries an ALT route: a correct expression with no errors scores M3, and the answer 88 then scores the A1, oe dep on M3

    Full marks: 4/4

    Question 24, Calculator allowed

    The diagram shows a square-based pyramid ABCDEABCDE.

    EABCDNot drawn accurately

    EA=EB=EC=EDEA = EB = EC = ED

    MM is the centre of the horizontal square base ABCDABCD
    QQ is the midpoint of ABAB
    Angle EQM=80EQM = 80^{\circ}

    EA:AB=n:1EA : AB = n : 1

    Work out the value of nn
    Give your answer correct to 33 significant figures. [4 marks]

    n =
    [Total 4 marks]
    Show solution & mark schemeHide solution & mark scheme

    Question 24 - Exam Solution

    Understanding the Question
    Given
    ABCDEABCDE is a square-based pyramid with EA=EB=EC=EDEA = EB = EC = ED.
    MM is the centre of the square base ABCDABCD, and that base is horizontal.
    QQ is the midpoint of ABAB.
    Angle EQM=80EQM = 80^{\circ}.
    The ratio EA:AB=n:1EA : AB = n : 1, so nn compares a sloping edge with a base edge.
    Find
    The value of nn, correct to 33 significant figures.
    Plan the Solution
    • A ratio does not care how big the pyramid is, so give the base the side length AB=1AB = 1. Then nn is simply the length EAEA.
    • All four sloping edges are equal, so EE sits directly above the centre MM. That makes EMEM vertical, so angle EMQ=90EMQ = 90^{\circ} and EQMEQM is a right-angled triangle carrying the 8080^{\circ}.
    • MM is the centre of the square and QQ is the midpoint of a side, so MQMQ is half a side. Cosine in triangle EQMEQM then gives EQEQ.
    • Triangle EABEAB is isosceles because EA=EBEA = EB, so the line from EE to the midpoint QQ is perpendicular to ABAB. Pythagoras in triangle EQAEQA finishes it.
    Worked Solution [4 marks]
    Rule - Right-angled triangles: cosθ=adjacenthypotenuse\cos \theta = \dfrac{\text{adjacent}}{\text{hypotenuse}} turns an angle into a side, and Pythagoras c2=a2+b2c^2 = a^2 + b^2 turns two sides into the third.
    Step 1 - Give the base a side length, then find MQMQ and AQAQ
    AB=1AB = 1
    MQ=12×1=0.5MQ = \dfrac{1}{2} \times 1 = 0.5
    AQ=12×1=0.5AQ = \dfrac{1}{2} \times 1 = 0.5
    EMQ0.580°EQEQA0.5EQEA
    (Reason: Only the ratio is asked for, so every side length gives the same nn. The centre of a square is half a side away from the midpoint of any side, which fixes MQMQ; and QQ is the midpoint of ABAB, which fixes AQAQ.)
    Step 2 - Use the right angle at MM to find EQEQ
    cos80=MQEQ\cos 80^{\circ} = \dfrac{MQ}{EQ}
    EQ=0.5cos80=2.87938EQ = \dfrac{0.5}{\cos 80^{\circ}} = 2.87938\ldots
    (Reason: Equal sloping edges put EE directly above MM, so EMEM is vertical and angle EMQEMQ is a right angle. In triangle EQMEQM the side MQMQ lies next to the 8080^{\circ} and EQEQ is the hypotenuse, so cosine is the ratio to use. Keep the unrounded value in the calculator.)
    Step 3 - Use the right angle at QQ to find EAEA
    EA2=EQ2+AQ2EA^2 = EQ^2 + AQ^2
    EA2=(2.87938)2+0.52=8.54085EA^2 = (2.87938\ldots)^2 + 0.5^2 = 8.54085\ldots
    EA=8.54085=2.92247EA = \sqrt{8.54085\ldots} = 2.92247\ldots
    (Reason: EA=EBEA = EB makes triangle EABEAB isosceles, so the line from EE to the midpoint QQ meets ABAB at a right angle. Triangle EQAEQA therefore has its right angle at QQ, with legs EQEQ and AQAQ. Watch which half-length belongs here: AQAQ is half a side, not half a diagonal.)
    Step 4 - Write the ratio, then round
    EA:AB=2.92247:1EA : AB = 2.92247\ldots : 1
    n=2.92247n = 2.92247\ldots
    n=2.92n = 2.92
    (Reason: Because ABAB was set to 11, the ratio EA:ABEA : AB is already in the form n:1n : 1, so nn is the length EAEA. Rounding to 33 significant figures is the last thing done, not the first.)
    n=2.92n = 2.92
    Verification
    Check 1 - work back to the angle the question gives: Start from the answer. With EA2=8.54085EA^2 = 8.54085\ldots and AQ=0.5AQ = 0.5, Pythagoras run backwards gives EQ=8.540850.25=2.87938EQ = \sqrt{8.54085\ldots - 0.25} = 2.87938\ldots, and then cosEQM=0.52.87938=0.17364\cos EQM = \dfrac{0.5}{2.87938\ldots} = 0.17364\ldots. Angle EQM=80EQM = 80^{\circ}, the angle the question states.
    Check 2 - reach the same edge up the axis instead of along the face: The vertical height is EM=0.5tan80=2.83564EM = 0.5 \tan 80^{\circ} = 2.83564\ldots, and AA is half a diagonal from the centre, so MA=0.52+0.52=0.70710MA = \sqrt{0.5^2 + 0.5^2} = 0.70710\ldots. Triangle EMAEMA has its right angle at MM, and it shares nothing with the route above except the given angle. EA=(2.83564)2+(0.70710)2=2.92247EA = \sqrt{(2.83564\ldots)^2 + (0.70710\ldots)^2} = 2.92247\ldots, the same length, so n=2.92n = 2.92 again.
    Check 3 - is the size sensible? The sloping edge must be longer than the slant height, which must be longer than MQMQ, and the three values do line up: 2.92247>2.87938>0.52.92247\ldots > 2.87938\ldots > 0.5. An angle of 8080^{\circ} is a steep face, so a sloping edge close to three times the base edge is what to expect. The three lengths are in the right order and the pyramid comes out tall and narrow, which is what 8080^{\circ} demands.
    Mark Scheme Breakdown
    StepMarkDescriptionGot it?
    1M1To find EQEQ: e.g. MQ=0.5(=AQ)MQ = 0.5 \, (= AQ), 0.5cos80(=2.87(938))\dfrac{0.5}{\cos 80} \, (= 2.87(938\ldots)); e.g. MQ=x(=AQ)MQ = x \, (= AQ), xcos80(=5.75x)\dfrac{x}{\cos 80} \, (= 5.75\ldots x). NB cos80=sin10\cos 80 = \sin 10.
    Or to find EMEM: e.g. MQ=0.5(=AQ)MQ = 0.5 \, (= AQ), 0.5tan80(=2.83(564))0.5 \tan 80 \, (= 2.83(564\ldots)); e.g. MQ=x(=AQ)MQ = x \, (= AQ), xtan80(=5.67x)x \tan 80 \, (= 5.67\ldots x). NB tan80=1tan10\tan 80 = \dfrac{1}{\tan 10}.
    Or to find EQEQ: e.g. EM=yEM = y, ysin80(=1.01y)\dfrac{y}{\sin 80} \, (= 1.01\ldots y); or to find MQ(=AQ)MQ \, (= AQ): e.g. EQ=hEQ = h, hcos80(=0.173h)h \cos 80 \, (= 0.173\ldots h).
    Notes: use of a value for the side ABAB, e.g. 11 or 2x2x or any value, or let EM=yEM = y or any value, or EQ=hEQ = h.
    2M1To find EA2EA^2: e.g. AQ=0.5(=MQ)AQ = 0.5 \, (= MQ), (2.87)2+0.52(=8.54(08))(2.87\ldots)^2 + 0.5^2 \, (= 8.54(08\ldots)); e.g. AQ=x(=MQ)AQ = x \, (= MQ), x2+(xcos80)2x^2 + \left(\dfrac{x}{\cos 80}\right)^2.
    Or to find AMAM: e.g. MQ=0.5(=AQ)MQ = 0.5 \, (= AQ), 0.52+0.52(=22=0.707(10))\sqrt{0.5^2 + 0.5^2} \, \left(= \dfrac{\sqrt{2}}{2} = 0.707(10\ldots)\right); e.g. MQ=x(=AQ)MQ = x \, (= AQ), x2+x2(=2x2=x2)\sqrt{x^2 + x^2} \, (= \sqrt{2x^2} = x\sqrt{2}).
    Or to find MQ(=AQ)MQ \, (= AQ): e.g. EM=yEM = y, ytan80(=0.176y)\dfrac{y}{\tan 80} \, (= 0.176\ldots y); then to find EA2EA^2: e.g. EQ=hEQ = h, h2+(hcos80)2h^2 + (h \cos 80)^2.
    A value the printed scheme shows in quotation marks may be the candidate's own earlier value.
    3M1To find EAEA: e.g. AQ=0.5(=MQ)AQ = 0.5 \, (= MQ), (2.87)2+0.52(=8.54(08))\sqrt{(2.87\ldots)^2 + 0.5^2} \, \left(= \sqrt{8.54(08\ldots)}\right); or e.g. AQ=x(=MQ)AQ = x \, (= MQ), x2+(xcos80)2(=5.84x)\sqrt{x^2 + \left(\dfrac{x}{\cos 80}\right)^2} \, (= 5.84\ldots x).
    Or e.g. AQ=0.5(=MQ)AQ = 0.5 \, (= MQ), (2.83)2+(0.707)2(=8.54(08))\sqrt{(2.83\ldots)^2 + (0.707\ldots)^2} \, \left(= \sqrt{8.54(08\ldots)}\right); e.g. AQ=x(=MQ)AQ = x \, (= MQ), (xtan80)2+(x2)2(=5.84x)\sqrt{(x \tan 80)^2 + (x\sqrt{2})^2} \, (= 5.84\ldots x).
    Or e.g. EM=yEM = y, (1sin80)2+(1tan80)2(=1.03y)\sqrt{\left(\dfrac{1}{\sin 80}\right)^2 + \left(\dfrac{1}{\tan 80}\right)^2} \, (= 1.03\ldots y), that is 1.03×AQ×tan801.03\ldots \times AQ \times \tan 80; e.g. EQ=hEQ = h, h2+(hcos80)2(=1.01h)\sqrt{h^2 + (h \cos 80)^2} \, (= 1.01\ldots h), that is 1.01×0.5cos801.01\ldots \times \dfrac{0.5}{\cos 80}.
    4A1Answer 2.922.92, awrt 2.922.92. Working not required, so a correct answer scores full marks unless it comes from obviously incorrect working.

    Full marks: 4/4

    Question 25, Calculator allowed

    (a) Express 28+24x6x228 + 24x - 6x^2 in the form ab(xc)2a - b(x - c)^2, where aa, bb and cc are integers. [3 marks]

    yxO

    (b) On the axes below, sketch the curve with equation y=28+24x6x2y = 28 + 24x - 6x^2
    Show clearly the coordinates of the turning point and the coordinates of the point where the curve meets the yy-axis. [3 marks]

    [Total 6 marks]
    Show solution & mark schemeHide solution & mark scheme

    Question 25 - Exam Solution

    Understanding the Question
    Given
    The expression 28+24x6x228 + 24x - 6x^2
    The form it must be written in, ab(xc)2a - b(x - c)^2, with aa, bb and cc integers
    A pair of blank axes for the sketch of y=28+24x6x2y = 28 + 24x - 6x^2
    Find
    (a) The completed square form, so the values of aa, bb and cc (b) The sketch, with the turning point and the point where the curve meets the yy-axis both labelled with their coordinates
    Plan the Solution
    • Write the expression in descending powers, so the x2x^2 term comes first.
    • Take the 6-6 out of the x2x^2 and xx terms only, and complete the square inside the bracket.
    • Multiply the 6-6 back in and collect the two constants, which gives ab(xc)2a - b(x - c)^2 straight away.
    • For part (b), read the turning point off that completed square, put x=0x = 0 in to find where the curve meets the yy-axis, and use the sign of the x2x^2 term to decide which way up the curve is.
    Worked Solution [6 marks]
    Rule - Completing the square with a negative x2x^2 term: take that coefficient out of the x2x^2 and xx terms first, complete the square inside the bracket, then multiply back in. In y=ab(xc)2y = a - b(x - c)^2 with bb positive, the square is never negative, so the curve has a maximum turning point at (c, a)(c,\ a).
    Step 1: Put the terms in descending powers and take out the 6-6
    28+24x6x2=6x2+24x+2828 + 24x - 6x^2 = -6x^2 + 24x + 28
    6x2+24x=6(x24x)-6x^2 + 24x = -6(x^2 - 4x)
    28+24x6x2=6(x24x)+2828 + 24x - 6x^2 = -6(x^2 - 4x) + 28
    (2, 52)(0, 28)yxO
    (Reason: Dividing 2424 by 6-6 gives 4-4, so the bracket is x24xx^2 - 4x. The 2828 has no xx in it, so it stays outside the bracket.)
    Step 2: Complete the square inside the bracket
    (x2)2=x24x+4(x - 2)^2 = x^2 - 4x + 4
    x24x=(x2)24x^2 - 4x = (x - 2)^2 - 4
    (Reason: Half of 4-4 is 2-2, so the bracket is (x2)2(x - 2)^2. Squaring that bracket brings in an extra 44, so 44 is taken away again to keep the value the same.)
    Step 3: Multiply the 6-6 back in and collect the constants
    6[(x2)24]+28=6(x2)2+24+28-6\left[(x - 2)^2 - 4\right] + 28 = -6(x - 2)^2 + 24 + 28
    24+28=5224 + 28 = 52
    28+24x6x2=526(x2)228 + 24x - 6x^2 = 52 - 6(x - 2)^2
    (Reason: Multiplying the 6-6 back in changes the sign of the 4-4 that sits inside the bracket, and the two constants outside are then collected into one.)
    Step 4: Read off the three integers
    ab(xc)2=526(x2)2a - b(x - c)^2 = 52 - 6(x - 2)^2
    a=52a = 52
    b=6b = 6
    c=2c = 2
    (Reason: All three are integers, which is what part (a) asks for. Note that bb is 66 and not 6-6, because the form already has a minus sign in front of the bb.)
    Step 5: (b) The turning point, straight from the completed square
    y=526(x2)2y = 52 - 6(x - 2)^2
    6(x2)206(x - 2)^2 \geq 0
    526×0=5252 - 6 \times 0 = 52
    (2, 52)(2,\ 52)
    (Reason: A square is never negative, so 6(x2)26(x - 2)^2 only takes away from the 5252. The largest value of yy therefore happens when the bracket is zero, at x=2x = 2, and there y=52y = 52. Because yy can never be more than this, the turning point is a maximum.)
    Step 6: (b) Where the curve meets the yy-axis
    28+24×06×02=2828 + 24 \times 0 - 6 \times 0^2 = 28
    (0, 28)(0,\ 28)
    (Reason: Every point on the yy-axis has x=0x = 0, so putting 00 in place of xx leaves the constant term, 2828.)
    Step 7: (b) Draw the sketch
    28+24×46×42=2828 + 24 \times 4 - 6 \times 4^2 = 28
    (0, 28)(2, 52)(4, 28)(0,\ 28) \quad (2,\ 52) \quad (4,\ 28)
    (Reason: The coefficient of x2x^2 is negative, so the curve opens downwards. It is symmetrical about the vertical line through the turning point, so the point level with (0, 28)(0,\ 28) on the other side is (4, 28)(4,\ 28). Draw one smooth curve through the three points, with the maximum at (2, 52)(2,\ 52), and label the turning point and the yy-axis crossing with their coordinates.)
    (a) 526(x2)252 - 6(x - 2)^2(b) a curve opening downwards, turning point (2, 52)(2,\ 52), meeting the yy-axis at (0, 28)(0,\ 28)
    Verification
    Check 1: Multiply the answer out again and compare it with the expression the question prints. 526(x24x+4)=526x2+24x24=28+24x6x252 - 6(x^2 - 4x + 4) = 52 - 6x^2 + 24x - 24 = 28 + 24x - 6x^2
    Check 2: Put x=1x = 1 into both forms. They are the same expression, so they must give the same value. 28+24×16×12=4628 + 24 \times 1 - 6 \times 1^2 = 46 and 526×(12)2=4652 - 6 \times (1 - 2)^2 = 46
    Check 3: Test the symmetry the sketch depends on. If the turning point really is at x=2x = 2, then x=0x = 0 and x=4x = 4 are the same distance from it and must give the same yy. 28+24×06×02=2828 + 24 \times 0 - 6 \times 0^2 = 28 and 28+24×46×42=2828 + 24 \times 4 - 6 \times 4^2 = 28
    Mark Scheme Breakdown
    StepMarkDescriptionGot it?
    (a) ±6(x±42)2\pm 6\left(x \pm \dfrac{4}{2}\right)^2 \ldots or ±6(x±2)2\pm 6(x \pm 2)^2 \ldots or ±6[(x±2)2]\pm 6\left[(x \pm 2)^2 \ldots\right] or ±6[(x±42)2]\pm 6\left[\left(x \pm \dfrac{4}{2}\right)^2 \ldots\right] or ±6(x±242×6)2\pm 6\left(x \pm \dfrac{24}{2 \times -6}\right)^2 \ldotsM1for a start to completing the square, or correct substitution into a(x+b2a)2+a\left(x + \dfrac{b}{2a}\right)^2 + \ldots from the formula a(x+b2a)2(b)24a+ca\left(x + \dfrac{b}{2a}\right)^2 - \dfrac{(b)^2}{4a} + c
    (a) 6[(x42)2(42)2]-6\left[\left(x - \dfrac{4}{2}\right)^2 - \left(\dfrac{4}{2}\right)^2\right] \ldots or 6[(x2)222]-6\left[(x - 2)^2 - 2^2\right] \ldots or 6[(x42)2(42)2]-6\left[\left(x - \dfrac{4}{2}\right)^2 - \left(\dfrac{4}{2}\right)^2 \ldots\right] or 6[(x2)222]-6\left[(x - 2)^2 - 2^2 \ldots\right] or 6(x+242×6)22424×6-6\left(x + \dfrac{24}{2 \times -6}\right)^2 - \dfrac{24^2}{4 \times -6} \ldotsM1for correctly completing the square, but terms do not need to be simplified and 2828 may or may not be present, or correct simplification of the first two parts of a(x+b2a)2(b)24a(+c)a\left(x + \dfrac{b}{2a}\right)^2 - \dfrac{(b)^2}{4a} (+c). NB: please refer to the ALT mark scheme after (b) for the comparison of coefficients method
    (a) 526(x2)252 - 6(x - 2)^2 - working not required, so a correct answer scores full marks (unless from obvious incorrect working)A1oe eg 6(x2)2+52-6(x - 2)^2 + 52
    (a) ALT bx2+2bcxbc2+a-bx^2 + 2bcx - bc^2 + a and b=6b = 6 or b=6b = -6M1for multiplying out ab(xc)2a - b(x - c)^2 and b=6b = 6 or b=6b = -6
    (a) ALT 2bc=242bc = 24 or bc2+a=28-bc^2 + a = 28M1for equating coefficients
    (a) ALT 526(x2)252 - 6(x - 2)^2 - working not required, so a correct answer scores full marks (unless from obvious incorrect working)A1oe eg 6(x2)2+52-6(x - 2)^2 + 52
    (b) a \cap or \cup shaped symmetrical quadratic curveB1for drawing a \cap or \cup shaped symmetrical quadratic curve with the turning point in any quadrant
    (b) turning point marked as (2, 52)(2,\ 52)B1for drawing a \cap shaped symmetrical quadratic curve in the correct quadrant with a turning point at (2, 52)(2,\ 52)
    (b) intersection with the yy-axis marked as (0, 28)(0,\ 28) or crossing at 2828 markedB1for drawing a \cap shaped symmetrical quadratic curve in the correct quadrant with an intersection on the yy-axis marked as (0, 28)(0,\ 28) or marked as 2828 on the yy-axis

    Full marks: 6/6

    Question 26, Calculator allowed

    Two solid candles, AA and BB, are mathematically similar.

    The height of candle AA is 3131 cm
    The height of candle BB is 18.618.6 cm

    Given that
    volume of candle Avolume of candle B=735 cm3\text{volume of candle } A - \text{volume of candle } B = 735 \text{ cm}^{3}

    work out the volume of candle AA [4 marks]

    cm³
    [Total 4 marks]
    Show solution & mark schemeHide solution & mark scheme

    Question 26 - Exam Solution

    Understanding the Question
    Given
    Two solid candles, AA and BB, that are mathematically similar.
    Height of candle AA: 3131 cm. Height of candle BB: 18.618.6 cm.
    volume of candle Avolume of candle B=735 cm3\text{volume of candle } A - \text{volume of candle } B = 735 \text{ cm}^{3}
    Neither volume is given on its own, only the gap between them.
    Find
    The volume of candle AA, in cubic centimetres.
    Plan the Solution
    • Divide the two heights to get the linear scale factor between the candles.
    • Cube it. A volume is three-dimensional, so the volume scale factor is the cube of the linear one.
    • Use it to write the volume of candle BB as a fraction of the volume of candle AA, so the given difference holds only one unknown.
    • Solve for the volume of candle AA, then rebuild both volumes and check the difference comes back to 735 cm3735 \text{ cm}^{3}.
    Worked Solution [4 marks]
    Rule for mathematically similar solids: if the linear scale factor is kk, the area scale factor is k2k^{2} and the volume scale factor is k3k^{3}.
    Step 1: Find the linear scale factor
    3118.6=310186=53\dfrac{31}{18.6} = \dfrac{310}{186} = \dfrac{5}{3}
    (Reason: Multiply top and bottom by 1010 to clear the decimal, then divide both by 6262. Candle AA is 53\dfrac{5}{3} times as tall as candle BB.)
    Step 2: Cube the scale factor to get the volume scale factor
    (53)3=12527\left( \dfrac{5}{3} \right)^{3} = \dfrac{125}{27}
    (35)3=27125\left( \dfrac{3}{5} \right)^{3} = \dfrac{27}{125}
    (Reason: A volume is three-dimensional, so every length being multiplied by 53\dfrac{5}{3} multiplies the volume by that factor three times over. The reversed fraction is the one that takes you from candle AA down to candle BB.)
    Step 3: Write candle B's volume in terms of candle A's
    VB=27125VAV_{B} = \dfrac{27}{125} V_{A}
    (Reason: Candle BB is the smaller solid, so its volume is the smaller share. Writing it this way leaves the given difference with only one unknown in it.)
    Step 4: Turn the given difference into an equation
    VA27125VA=735V_{A} - \dfrac{27}{125} V_{A} = 735
    127125=981251 - \dfrac{27}{125} = \dfrac{98}{125}
    98125VA=735\dfrac{98}{125} V_{A} = 735
    (Reason: The question gives the gap between the volumes, not either volume, so substitute for VBV_{B} and collect the VAV_{A} terms. The gap is 98125\dfrac{98}{125} of candle AA.)
    Step 5: Solve for the volume of candle A
    VA=735×12598V_{A} = 735 \times \dfrac{125}{98}
    73598=7.5\dfrac{735}{98} = 7.5
    7.5×125=937.57.5 \times 125 = 937.5
    (Reason: Read it as parts: candle AA is 125125 parts and candle BB is 2727 of them, so the 9898 parts in between are worth 735 cm3735 \text{ cm}^{3}. One part is 7.5 cm37.5 \text{ cm}^{3}, so all 125125 parts are 937.5 cm3937.5 \text{ cm}^{3}.)
    937.5 cm3937.5 \text{ cm}^{3}
    Verification
    Check 1: Scale the answer back down to candle BB with the volume scale factor 27125\dfrac{27}{125}, then take the difference the question gives. 937.5×27125=202.5937.5 \times \dfrac{27}{125} = 202.5 and 937.5202.5=735937.5 - 202.5 = 735
    Check 2: Redo it without ever simplifying the ratio, working straight from the cubed heights 313=2979131^{3} = 29791 and 18.63=6434.85618.6^{3} = 6434.856. 29791×735297916434.856=937.5\dfrac{29791 \times 735}{29791 - 6434.856} = 937.5
    Check 3: Volume divided by height cubed must be the same constant for both candles, since they are mathematically similar. 937.529791=202.56434.856\dfrac{937.5}{29791} = \dfrac{202.5}{6434.856}
    Mark Scheme Breakdown
    StepMarkDescriptionGot it?
    A:B=31:18.6(=5:3)A : B = 31 : 18.6 \, (= 5 : 3) oe or A3:B3=313:18.63(=53:33)A^{3} : B^{3} = 31^{3} : 18.6^{3} \, (= 5^{3} : 3^{3}) oe or 3118.6(=53)\dfrac{31}{18.6} \left( = \dfrac{5}{3} \right) oe or 18.631(=35)\dfrac{18.6}{31} \left( = \dfrac{3}{5} \right) oe or (18.631)3\left( \dfrac{18.6}{31} \right)^{3} oe or 27125\dfrac{27}{125} oe or (3118.6)3\left( \dfrac{31}{18.6} \right)^{3} oe or 12527\dfrac{125}{27} oeM1for correct linear SF or volume SF either as a fraction or ratio. Allow 53=1.6(6....)\dfrac{5}{3} = 1.6(6....) truncated or rounded
    VA(35)3VA(=735)V_{A} - \left( \dfrac{3}{5} \right)^{3} V_{A} \, (= 735) oe or VA27125VA(=735)V_{A} - \dfrac{27}{125} V_{A} \, (= 735) oe or 98125VA(=735)\dfrac{98}{125} V_{A} \, (= 735) oe or VAVA735=31318.63\dfrac{V_{A}}{V_{A} - 735} = \dfrac{31^{3}}{18.6^{3}} oe or (53)3VBVB(=735)\left( \dfrac{5}{3} \right)^{3} V_{B} - V_{B} \, (= 735) oe or 12527VBVB(=735)\dfrac{125}{27} V_{B} - V_{B} \, (= 735) oe or 9827VB(=735)\dfrac{98}{27} V_{B} \, (= 735) oe or VB+735VB=31318.63\dfrac{V_{B} + 735}{V_{B}} = \dfrac{31^{3}}{18.6^{3}} oe or 1(35)3(=98125=0.784)1 - \left( \dfrac{3}{5} \right)^{3} \left( = \dfrac{98}{125} = 0.784 \right) oe or (53)31(=9827=3.62(962...))\left( \dfrac{5}{3} \right)^{3} - 1 \left( = \dfrac{98}{27} = 3.62(962...) \right) oe or 5333(=12527=98)5^{3} - 3^{3} \, (= 125 - 27 = 98)M1Note: 735735 is given in the equation. Allow any letter for VAV_{A} or for VBV_{B}. VA(35)3VA(=735)V_{A} - \left( \dfrac{3}{5} \right)^{3} V_{A} \, (= 735) can be written as VAVA(53)3(=735)V_{A} - \dfrac{V_{A}}{\left( \dfrac{5}{3} \right)^{3}} \, (= 735), or (53)3VBVB(=735)\left( \dfrac{5}{3} \right)^{3} V_{B} - V_{B} \, (= 735) can be written as VB(35)3VB(=735)\dfrac{V_{B}}{\left( \dfrac{3}{5} \right)^{3}} - V_{B} \, (= 735)
    (VA=)735×12598(V_{A} =) \, 735 \times \dfrac{125}{98} oe or (VA=)73598125(V_{A} =) \, \dfrac{735}{\dfrac{98}{125}} oe or (VA=)313×73531318.63(V_{A} =) \, \dfrac{31^{3} \times 735}{31^{3} - 18.6^{3}} oe or (VB=)735×2798(=202.5)(V_{B} =) \, 735 \times \dfrac{27}{98} \, (= 202.5) oe or (VB=)7359827(=202.5)(V_{B} =) \, \dfrac{735}{\dfrac{98}{27}} \, (= 202.5) or (VB=)18.63×73531318.63(=202.5)(V_{B} =) \, \dfrac{18.6^{3} \times 735}{31^{3} - 18.6^{3}} \, (= 202.5) oe or 73598×53\dfrac{735}{98} \times 5^{3} oe or 7.5×1257.5 \times 125 oe or 73598×33(=202.5)\dfrac{735}{98} \times 3^{3} \, (= 202.5) oe or 7.5×27(=202.5)7.5 \times 27 \, (= 202.5) oeM1for a correct method to find VAV_{A} or VBV_{B}
    937.5937.5 (working not required, so a correct answer scores full marks unless it comes from obvious incorrect working)A1oe allow 938938 from correct working

    Full marks: 4/4

    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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