Engineering Board Exam Reviewer · Permutations · medium

If nP2=56, find n.

  1. 7
  2. 9
  3. 8
  4. 28

Answer

C. 8

Solution

nP2=n(n-1)=56 n2-n-56=0 (n-8)(n+7)=0. So n=8.

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