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Question
Evaluate `(n!)/((n-r)!)`, when n = 9, r = 5
Solution
When n = 9, r = 5 `(n!)/((n-r)!) = (9!)/((9 - 5)!) = (9!)/(4!) = (9 xx 8 xx 7 xx 6 xx 5 xx 4!)/(4!)`
= 9 x 8 x 7 x 6 x 5 = 15120
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