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Evaluate : n!r!(n-r)! for n = 12, r = 12

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Question

Evaluate : `("n"!)/("r"!("n" - "r")!)` for n = 12, r = 12

Sum
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Solution

n = 12, r = 12

∴ `("n"!)/("r"!("n" - "r")!) = (12!)/(12!(12 - 12)!)` 

= `(12!)/(12!  0!)`

= 1    ...[∵ 0! = 1]

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Chapter 3: Permutations and Combination - Exercise 3.2 [Page 49]

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