emilem wrote:

sparky wrote:

krishrads wrote:

There are 12 girls and 15 boys in a class.In how many ways can we form 4 pairs for a dance?

Thanks

let's see

(12c4)(15c4)*4!

sparky, why to multiply with 4!? Isn't it just (12C4)*(15C4)

you multiply by 4! to count the different ways to arrange the pairs. it is (12C4)*(15C4) to count the ways to choose the boys/girls from their respective groups. we have 4 spaces for 4 pairs. 1st space is 4 ways, 2nd space is 3 ways and so on...

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