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WAEC Mathematics 2018 Question 46

Question 46

Sets

M and N are two subsets of the universal set (U). If n(U) = 48, n(M) = 20, n(N) = 30 and n(M ∪ N) = 40, find n(M ∩ N)′.

  1. A.18
  2. B.20
  3. C.30
  4. D.38
Show the answer and explanation

Answer: D (38)

Explanation

n(M ∩ N) = 20 + 30 − 40 = 10, so n(M ∩ N)′ = 48 − 10 = 38.