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0580/12 May/Jun 2021, Question 13: Reciprocals

Cambridge IGCSE Mathematics 0580 · Paper 12 (Core) · Calculator · 3 marks

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The question, in short

Complete two short statements about a reciprocal and a prime, then pick an irrational number from a given list of five values.

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Part (a) · 2 marks

Fill in the missing value for the reciprocal of 0.2 and name a prime number lying between 90 and 100.

  1. 1Reciprocal of 0.2 = 1 ÷ 0.2 = 5
  2. 2Primes between 90 and 100: 97 (91 = 7 × 13, 93 = 3 × 31, 95, 99 are not prime)
  3. 3Answers: 5, 97

Answer5, 97

Part (b) · 1 mark

From the list 7/5, 0.6, √7, 8, √9, choose and write the one irrational number.

  1. 1√9 = 3 and 7/5, 0.6, 8 are rational
  2. 2√7 cannot be written as a fraction, so the irrational number is √7

Answer√7

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