Question Bank › GCSE Algebra › Substitution
Substitution Topic Simplifying Basic Expressions (17) Expanding Brackets (13) Substitution (10) Drawing & Using Graphs (34) Solving Simple Equations (21) Factorising (9) Algebraic Fractions (4) Linear Graphs & Gradients (26) Forming Equations (15) Solving Quadratics (10) Quadratic Inequalities (2) Linear Inequalities (9) Simultaneous Equations (9) Completing the Square (2) Functions (9) Graphical Transformations (2) Indices (14) Manipulating Formulae/ Changing the Subject (9) Sequences (19) Iterations (1) Current PowerPoint version
All boards Edexcel AQA All specs Current spec All series June 2025 November 2024 June 2024 November 2023 June 2017 Any marks 1 to 4 marks 5 to 8 marks 9+ marks
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Foundation June 2025 Paper 2 Q7 7 Here is a rule to work out the cost of buying a number of floorboards.
Cost = £55 \(\times\) number of floorboards
Toby buys a number of floorboards. The cost is £330
Work out the number of floorboards Toby buys. (2)
Mark scheme
Mark scheme Answer Mark Mark scheme 6 M1 for \(330 \div 55\) A1 cao
Additional guidance Build up methods are allowed Condone one error in build up method \(55 \times 6 = 330\), 330 or 55 on answer line scores M1A0
ignore use of £ eg £6
Foundation June 2025 Paper 1 Q16 16
(a) \[d = \frac{800}{w}\]
\(d\) represents the number of days to complete a job. \(w\) represents the number of workers needed. Assume the job needs completing in 20 days.
How many workers are needed? [3 marks]
(b) In fact, the job needs completing in
fewer than 20 days.
What does this mean about the number of workers that are needed?
Tick one box. [1 mark]
It is less than the answer to part (a) It is the same as the answer to part (a) It is greater than the answer to part (a) Mark scheme (a) Mark scheme (b)
Mark scheme (a) Answer Mark Comments \(20 = \dfrac{800}{w}\) or \((w =)\ \dfrac{800}{d}\) M1 oe \(800 \div 20\) M1dep oe 40 A1
Mark scheme (b) Answer Mark Comments It is greater than the answer to part (a) B1
Foundation June 2025 Paper 1 Q10 10 Work out the value of \(\quad 2(a^2 + 3a) \quad\) when \(\quad a = 4\) [3 marks]
Mark scheme
Mark scheme Answer Mark Comments Alternative method 1: substitutes first \(4^2\) or 16 or 32 or \(3 \times 4\) or 12 or 24 M1 oe implied by 28 \(2 \times (4 \times 4 + 3 \times 4)\) M1dep oe 56 A1 Alternative method 2: multiplies out first \(2 \times a^2\) or \(2 \times 3a\) M1 oe \(2 \times 4 \times 4 + 2 \times 3 \times 4\) M1dep oe 56 A1 Alternative method 3: factorises first \(2a(a + 3)\) or \(2 \times a\) or \(a + 3\) M1 oe \(2 \times 4 \times (4 + 3)\) M1dep oe 56 A1
Additional guidance Inclusion of \(a\) can score a maximum of one mark eg1 \(4^2 = 16 \quad 16 \times 2 = 32a\) eg2 \(56a\) M1 only M1 only \(2 \times 4^2 + 2 \times 3a\) is not enough for the second mark of Alt 2 M1M0A0
Foundation November 2024 Paper 3 Q23 23 The total cost of a taxi ride is calculated by adding
a fixed charge of £4 and a charge of £2 per mile.
Write a formula to work out the total cost, £\(C\), of a journey of \(m\) miles. [2 marks]
Mark scheme
Mark scheme Answer Mark Comments \(2m + 4\) or \(2 \times m + 4\) B2 oe B1 \(2m\) or \(m2\) or \(200m + 400\) or \(km + 4\) with k an integer, \(k \ne 0\) or 2
Additional guidance Ignore any attempt to substitute a value for \(m\) after \(2m\) seen for B1 Condone \(m2 + 4\) (not testing simplification) B2 Accept use of another letter for \(m\) other than \(c\) eg1 \(2x + 4\) eg2 \(2c + 4\) B2 B0Condone inclusion of £ sign for B1 eg1 £\(2m + 4\) eg2 £\(2m\) B1 B1
Foundation November 2024 Paper 2 Q12 12
(a) Work out the value of \(\quad x^2 + 7x \quad\) when \(\quad x = -4\) [2 marks]
(b) Rearrange \(\quad y = w - 1 \quad\) to make \(w\) the subject. [1 mark]
(c) Simplify fully \(\quad 4(a + 2) + a\) [2 marks]
Mark scheme (a) Mark scheme (b) Mark scheme (c)
Mark scheme (a) Answer Mark Comments \((-4)^2 + 7 \times -4\) or \(-4(-4 + 7)\) or 16 or \(-28\) M1 oe eg \((-4)^2 + 7(-4)\) \(-12\) A1 SC1 \(-44\)
Additional guidance SC is for \(-4^2 + 7 \times -4 = -16 - 28 = -44\) Embedded 16 or \(-28\) seen eg \(16 + 7x\) without correct answer M1A0 Values may be implied eg1 \((-4)^2 + 7 \times 4 = 44\) 16 is implied eg2 only answer 44 M1A0 M0A0Further correct work eg \(16 - 28 = -12\), Answer \(3x\) M1A1 Further incorrect work eg \(16 - 28 = -12\), Answer \(-12x\) M1A0 \(+-28\) is the same as \(-28\) M1 Only \(-4^2 + 7 \times -4\) M0A0 \(-4^2 + 7 \times -4 = -16 + 28 = 12\) M0A0 \(16x\) does not imply 16 M0A0
Mark scheme (b) Answer Mark Comments \(y + 1\) or \(1 + y\) B1
Mark scheme (c) Answer Mark Comments \(4a + 8\) or \(8 + 4a\) or \(5a\) M1 \(5a + 8\) or \(8 + 5a\) A1
Additional guidance Further incorrect work or simplification eg \(5a + 8\), Answer \(13a\) M1A0
Foundation June 2024 Paper 1 Q11 11 A window cleaner uses this formula.
\(C\) = cost, in £, for the customer \(W\) = number of windows to be cleaned
(a) How much does it cost for 6 windows to be cleaned? [2 marks]
(b) The cost for another customer was £24
Show why this cost must be incorrect. [1 mark]
Mark scheme (a) Mark scheme (b)
Mark scheme (a) Answer Mark Comments \(2 \times 6\) or 12 or 1700 M1 oe 17(.00) A1 accept 1700p
Mark scheme (b) Answer Mark Comments 9.5 or \(9\frac{1}{2}\) or valid reason B1 eg shows that 9 windows cost £23 and 10 windows cost £25 or you can’t have half a window
Additional guidance Calculated values must be correct (19, 21,) 23, 25 (, 27…) B1 Even number \(+\) 5 can’t be even / can’t end in a 4 B1 There’s no whole number you can times by 2 to get to 19 There’s no number you can times by 2 to get to 19 B1 B0 Even \(+\) 5 \(=\) odd, 24 is even Even \(+\) 5 \(=\) odd B1 B0 Costs are all always odd numbers, 24 is even Costs are all always odd numbers B1 B0 19 is a prime number and so doesn’t divide exactly by 2 19 is a prime number B1 B0
Foundation November 2023 Paper 3 Q5 5
(a) \(d = g^2 - 2h\)
Work out the value of \(d\) when \(\quad g = 15 \quad\) and \(\quad h = 63\) [2 marks]
(b) Rearrange \(\quad m = n + k \quad\) to make \(n\) the subject. [1 mark]
Mark scheme (a) Mark scheme (b)
Mark scheme (a) Answer Mark Comments \(15^2 - 2 \times 63\) or 225 or 126 M1 \(-126\) implies M1 99 A1
Mark scheme (b) Answer Mark Comments \(m - k\) or \(-k + m\) B1
Foundation June 2017 Paper 3 Q19 19 The value of \(x\) can be 2 or 5
The value of \(y\) can be 3 or 12
(a) List the possible values of \(\quad xy\) [2 marks]
(b) Work out the
least possible value of \(\quad \dfrac{x - y}{x}\)
You must show your working. [2 marks]
Mark scheme (a) Mark scheme (b)
Mark scheme (a) Answer Mark Comments 6, 15, 24, 60 in any order B2 B1 for 6, 15, 24, 60 with no more than one additional value or three correct values with no more than one incorrect value
Additional guidance Ignore repeated values for B2 and B1 6, 10, 15, 24, 60 B1 6, 10, 15, 24 B1 6, 10, 15, 24, 36 B0 \(2 \times 3,\ 5 \times 3,\ 2 \times 12,\ 5 \times 12\) B0 \(6xy,\ 15xy,\ 24xy,\ 60xy\) B0
Mark scheme (b) Answer Mark Comments \(\dfrac{2 - 12}{2}\) or one correctly evaluated trial with correct substitutions for \(x = 2\) or 5 and \(y = 3\) or 12 or two correct values from \(-\dfrac{10}{2},\ -\dfrac{1}{2},\ -\dfrac{7}{5},\ \dfrac{2}{5}\) oe or two correct values from \(-5,\ -0.5,\ -1.4,\ 0.4\) oe M1 \(\dfrac{2 - 3}{2} = -\dfrac{1}{2}\) oe or \(\dfrac{5 - 12}{5} = -\dfrac{7}{5}\) oe or \(\dfrac{5 - 3}{5} = \dfrac{2}{5}\) oe \(-\dfrac{10}{2}\) or \(-5\) A1
Additional guidance Two separate correct values can be in either fraction or decimal form \(2 - 12 \div 2 = -5\) (recovered) M1A1 \(2 - 12 \div 2\) M0A0 An example of an incorrect substitution with different values of \(x\) eg \(\dfrac{5 - 12}{2} = -\dfrac{7}{2}\)
Foundation June 2017 Paper 1 Q12 12 A football team has \(P\) points.
\[P = 3W + D\]
\(W\) is the number of wins
\(D\) is the number of draws
(a) A team has 6 wins and 2 draws.
How many points does the team have? [1 mark]
(b) After 33 games a different team has 53 points.
11 games were draws.
How many games has this team lost ? [4 marks]
Mark scheme (a) Mark scheme (b)
Mark scheme (a) Answer Mark Comments 20 B1 allow \(P = 20\)
Mark scheme (b) Answer Mark Comments \(53 - 11\) or 42 or \(33 \times 3\) or 99 or \(11 \times 2\) or \(33 - 11\) or 22 M1 their 42 \(\div\) 3 or 14 or their 99 \(-\) 53 \(-\) their 22 or (their 22 \(\times\) 3) \(-\) their 42 or 24 M1dep oe eg build up - allow one error \(33 - 11 -\) their 14 or their 24 \(\div\) 3 M1dep dep on M1M1 8 A1
Additional guidance \(3 \times 14 + 11 = 53\) M2
Foundation June 2017 Paper 3 Q7 7 Here is a number machine.
(a) Work out the output when the input is 4 [1 mark]
(b) Work out the output when the input is –4 [1 mark]
Mark scheme (a) Mark scheme (b)
Mark scheme (a) Mark scheme (b) No questions match these filters.