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JAMB Mathematics 2000 Question 45

Question 45

Probability

If U = {x : x is an integer and 1 ≤ x ≤ 20}, E1 = {x : x is a multiple of 3}, E2 = {x : x is a multiple of 4} and an integer is picked at random from U, find the probability that it is not in E2.

  1. A.3/4
  2. B.3/10
  3. C.1/4
  4. D.1/20
Show the answer and explanation

Answer: A (3/4)

Explanation

The multiples of 4 from 1 to 20 are 4, 8, 12, 16, 20: five numbers. So 15 of the 20 are not in E2, a probability of 15/20 = 3/4.