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4024/12 May/Jun 2026, Question 11: Prime factors and HCF

Cambridge O Level Mathematics 4024 · Paper 12 (Non-calculator) · Non-calculator · 4 marks

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The question, in short

Express 400 as a product of prime factors, then find the highest common factor of 400 and 180.

Summarised in our own words. Use the official paper for the exact wording and any diagrams.

Part (a) · 2 marks

Write 400 as a product of primes.

  1. 1400 = 2 × 200 = 2 × 2 × 100
  2. 2100 = 2 × 2 × 5 × 5
  3. 3400 = 2⁴ × 5²

Answer2⁴ × 5² or 2 × 2 × 2 × 2 × 5 × 5

Part (b) · 2 marks

Find the HCF of 400 and 180.

  1. 1180 = 2² × 3² × 5
  2. 2400 = 2⁴ × 5²
  3. 3HCF = 2² × 5 = 20

Answer20

Stuck on a step? Read the free lesson: Prime Factorization

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