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WAEC Further Mathematics 2018 Question 16

Question 16

Permutations and Combinations

How many numbers greater than 150 can be formed from the digits 1, 2, 3, 4, 5 if no repetition is allowed?

  1. A.91
  2. B.191
  3. C.291
  4. D.391
Show the answer and explanation

Answer: C (291)

Explanation

3-digit: first digit 2–5 gives 4 × 4 × 3 = 48, and 152, 153, 154 add 3 (total 51). 4-digit: 5 × 4 × 3 × 2 = 120. 5-digit: 120. Total 291.