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0580/23 Oct/Nov 2025, Question 7: Prime Numbers

Cambridge IGCSE Mathematics 0580 · Paper 23 (Extended) · Non-calculator · 3 marks

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The question, in short

Find sums involving prime numbers: one below 16, and one giving a possible integer x where primes between 6 and x total 18.

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Part (a) · 2 marks

Find the sum of all prime numbers less than 16.

  1. 1Primes less than 16: 2, 3, 5, 7, 11, 13
  2. 217 + 11 + 13 = 41

Answer41

Part (b) · 1 mark

Given integer x, the primes greater than 6 and less than x sum to 18; find a possible x.

  1. 1Primes greater than 6: 7, 11, 13, …; 7 + 11 = 18
  2. 2x must be greater than 11 but not greater than 13, so x = 12 or 13

Answer12 or 13

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Also searched as: 0580/23/O/N/25 · 0580_w25_qp_23 · 0580 w25 23 · question 7.
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