Combinations and permutations?

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Please show me how. Thanks

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Answer 1 · 2018-04-20T00:16:30

#1/432#

First you need to know that for a permutation, the general formula is:

#P_(n,k)=(n!)/((n-k)!); n="population", k="picks"#

and for a combination, it's

#C_(n,k)=(n!)/((k!)(n-k)!)# with #n="population", k="picks"#

We can then use these and substitute in the numbers:

#((12!)/((9!)(3!)))/((12!)/((7!)))#

#((12!)/((9!)(3!)))xx((7!)/(12!))#

#(7!)/((9!)(3!)#

#(7!)/((9xx8xx7!)(3!)#

#1/((9xx8)(6))=1/432#