Integers, Factors, Multiples and Primes: Edexcel 4MA1 Past Paper Questions and Worked Solutions
This page collects every integers, factors, multiples and primes question from the Pearson Edexcel International GCSE Mathematics A (4MA1) Higher tier Paper 1H and Paper 1HR, January 2020 to June 2025: 12 questions worth 38 marks. Questions run from easier to harder. Try each one first, then click “Show solution” for a step-by-step method with the reason for every step. All answers are checked against the official Pearson mark schemes.
Write 2250 as a product of powers of its prime factors. Show your working clearly.
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- Keep dividing by prime numbers: 2250 ÷ 2 = 1125, 1125 ÷ 3 = 375, 375 ÷ 3 = 125, 125 ÷ 5 = 25, 25 ÷ 5 = 5, 5 ÷ 5 = 1
- So 2250 = 2 × 3 × 3 × 5 × 5 × 5
- Write repeated factors as powers.
Answer: 2 × 32 × 53
Find the lowest common multiple (LCM) of 45 and 70.
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- Write each number as a product of prime factors: 45 = 32 × 5 and 70 = 2 × 5 × 7
- The LCM uses every prime that appears, each with its highest power: 2 × 32 × 5 × 7
- 2 × 9 × 5 × 7 = 630
Answer: 630
Find the lowest common multiple (LCM) of 28 and 105.
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- 28 = 22 × 7 and 105 = 3 × 5 × 7
- LCM: every prime with its highest power: 22 × 3 × 5 × 7 = 4 × 105
Answer: 420
(a) Find the highest common factor (HCF) of 56 and 84. Show your working clearly. (2)
(b) Find the lowest common multiple (LCM) of 60 and 72. Show your working clearly. (2)
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Part (a)
- 56 = 23 × 7 and 84 = 22 × 3 × 7
- HCF: the shared primes with their lowest powers: 22 × 7
Answer: 28
Part (b)
- 60 = 22 × 3 × 5 and 72 = 23 × 32
- LCM: every prime with its highest power: 23 × 32 × 5 = 8 × 9 × 5
Answer: 360
Find the highest common factor (HCF) of 72 and 108. Show your working clearly.
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- Write each number as a product of prime factors.
- 72 = 2 × 2 × 2 × 3 × 3 = 23 × 32
- 108 = 2 × 2 × 3 × 3 × 3 = 22 × 33
- The HCF uses only the primes the two numbers share, each with its lowest power: 22 × 32
- 22 × 32 = 4 × 9
Answer: 36
(a) Work out the lowest common multiple (LCM) of 36 and 120 (2)
A = 52 × 74 × 11p and B = 5m × 7n−5 × 11, where m, n and p are integers such that m > 2, n > 10 and p > 1
(b) Find the highest common factor (HCF) of A and B. Give your answer as a product of powers of its prime factors. (2)
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Part (a)
- 36 = 22 × 32 and 120 = 23 × 3 × 5
- LCM = 23 × 32 × 5 = 8 × 9 × 5
Answer: 360
Part (b)
- The HCF uses the lower power of each prime.
- 5: m > 2, so 52 is the lower power. 7: n − 5 > 5, so 74 is lower. 11: p > 1, so 111 is lower.
Answer: 52 × 74 × 11
Write 3.6 × 103 as a product of powers of its prime factors. Show your working clearly.
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- 3.6 × 103 = 3600
- 3600 = 36 × 100 = (22 × 32) × (22 × 52)
- Collect the powers of each prime.
Answer: 24 × 32 × 52
(a) Write 300 as a product of its prime factors. Show your working clearly. (2)
A = 2 × 2 × 2 × 3 × 3 × 5 and B = 2 × 2 × 3 × 3 × 3 × 5
(b) Find the lowest common multiple (LCM) of 5A and 7B. Show your working clearly. (2)
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Part (a)
- Divide by primes: 300 = 2 × 150 = 2 × 2 × 75 = 2 × 2 × 3 × 25 = 2 × 2 × 3 × 5 × 5
Answer: 22 × 3 × 52
Part (b)
- 5A = 23 × 32 × 52 and 7B = 22 × 33 × 5 × 7
- The LCM takes every prime with its highest power: 23 × 33 × 52 × 7
- 8 × 27 × 25 × 7 = 37 800
Answer: 37 800 (= 23 × 33 × 52 × 7)
A = 28 × 35 × 114 and B = 26 × 3 × 118
(a) Find the highest common factor (HCF) of A and B. (2)
(b) Find the lowest common multiple (LCM) of 2A and 3B. Give the LCM as a product of powers of its prime factors. (2)
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Part (a)
- Lowest power of each prime: 26, 31, 114
Answer: 26 × 3 × 114
Part (b)
- 2A = 29 × 35 × 114 and 3B = 26 × 32 × 118
- Highest power of each prime: 29, 35, 118
Answer: 29 × 35 × 118
A = 2 × 343 and B = 16 × 337
(a) Find the highest common factor (HCF) of A and B. (1)
(b) Express the number A × B as a product of powers of its prime factors. Give your answer in its simplest form. (2)
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Part (a)
- Write 16 as 24, so B = 24 × 337. The HCF uses the lowest powers: 21 and 337.
Answer: 2 × 337
Part (b)
- A × B = 2 × 343 × 24 × 337 = 21+4 × 343+37
Answer: 25 × 380
A = 25 × 5 × 72 and B = 23 × 53 × 74
(a) Write down the highest common factor (HCF) of 5A and 2B. Give your answer as a product of prime factors. (2)
(b) Work out the value of (AB)2. Give your answer as a product of prime factors. (2)
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Part (a)
- 5A = 25 × 52 × 72 (one more 5) and 2B = 24 × 53 × 74 (one more 2).
- The HCF takes each prime with its lowest power: 24, 52 and 72
Answer: 24 × 52 × 72
Part (b)
- AB: add the powers of each prime. 25+3 × 51+3 × 72+4 = 28 × 54 × 76
- Squaring doubles every power.
Answer: 216 × 58 × 712
P = 33 × 52 × 7 and Q = 32 × 5 × 72
(a) Write down the highest common factor (HCF) of P and Q. (1)
(b) Work out the value of P3 × Q. Give your answer in the form 3x × 5y × 7z where x, y and z are positive integers. (2)
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Part (a)
- Take each prime with its lowest power: 32, 51, 71
Answer: 32 × 5 × 7 (= 315)
Part (b)
- P3: multiply every power by 3: 39 × 56 × 73
- Multiply by Q: add the powers of each prime: 39+2 × 56+1 × 73+2
Answer: 311 × 57 × 75
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