Solve for n: P(n,3) = 6P (n-1,2)

Question

Permutations question from a quiz review sheet (Gr. 12 Data Management)

Answer 1

 

P(n,3) = n!/(n-3)! = 6P(n-1,2) = 6(n-1)!/(n-3)!

               

Multiply both sides (bold items) by (n-3)!

n! = 6(n-1)!

n(n-1)! = 6(n-1)!

Divide both sides by (n-1)!  (or compare the two sides and notice n=6)

n=6