Skip to content

CMA Foundation · Fundamentals of Business Mathematics and Statistics · Permutation and Combinations

If nP2 = 90, find the value of n, where n is a positive integer.

The value of n is 10. Since nP2 equals n(n − 1), setting n(n − 1) = 90 gives n² − n − 90 = 0, which factors as (n − 10)(n + 9) = 0. The positive solution is n = 10.

  1. A8
  2. B9
  3. C10Correct
  4. D12

Explanation

nP2 = n(n − 1) = 90. Since 10 × 9 = 90, n = 10. Check: 9 × 8 = 72 is not 90, and 12 × 11 = 132 is not 90.

Did you get it right without looking?

One question tells you little. A timed set on Permutation and Combinations shows your real accuracy, how long you take and where you lose marks.

Practise Permutation and CombinationsFree diagnostic mock

More Permutation and Combinations questions