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WAEC Further Mathematics 2020 Question 32

Question 32

Permutations and Combinations

A three − digit odd number less than 500 is to be formed from 1, 2, 3, 4 and 5. If repetition of digits is allowed, in how many ways can this be done?

  1. A.125
  2. B.75
  3. C.60
  4. D.36
Show the answer and explanation

Answer: C (60)

Explanation

First digit 1–4 (4 ways, to stay below 500), middle digit any of 5, last digit 1, 3 or 5 (3 ways): 4 × 5 × 3 = 60.