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JAMB 1986 · UME · Q47

Find the probability that a number selected at random from 40 to 50 is a prime.

Worked solution (try it first)
  1. From 40 to 50 inclusive there are 50−40+1=1150 - 40 + 1 = 11 numbers.
  2. The primes among them are 41, 43 and 47.
  3. 49 is 7×77 \times 7.
  4. So the probability is 311\frac{3}{11}, option A.

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