Question

find the value of
i) 15 p 3
ii) 39 c 3

Answer 1

15p3= 15!/(15-3)!=15×14×13×12!/12!=15×14×13 ans

ii) 39c3= 39!/(3!)(39-3)!=39×38×37×36!/3!×36!
=39×38×37/3!=39×38×37/6=13×19×37 ans

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Answer 2

1) 15p3

nPr = n!/(n-r)!
= 15!/(15-3)!
= 15×14×13×12!/ 12! (cancel 12!)
=15×14×13
= 2730

2) 39c3

nCr = n!/r!(n-r)!
= 39!/3!(39-3)!
= 39×38×37×36!/3! × 36!(cancel 36!)
= 39×38×37/ 3×2
= 9139