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Grade 12 Permutations

  • Thread starter zenity
  • Start date
  • #1
13
0
Was just wondering if there was a "shorter" method of solving this problem.

nPr = 60.

nPr = n!/(n-r)!

n=?
r=3

Works out to be

n(n-1)(n-2) = 60.

From here on, what different options do I have? I have several ways of solving it, but was wondering what would be the "easiest" method.
 

Answers and Replies

  • #2
609
0
since n is integer, find all the factors of 60, which are 2,3,4,5 and see which 3 consecutive numbers satisfy n(n-1)(n-2)=60
 

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