1] (6 choose 4)*(5 choose 3) * 7!

2] (6 choose 4)*(5 choose 3) * 4

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3] (6 choose 4) * (5 choose 3) * 3! * 4!

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(6 choose 4) = 6!/( 4! 2!) = 6*5/2 = 15

(5 choose 3) = 5!/(3!2!) = 5*4/2 = 10

you can now use your calculator to finish them off

Jaehyun J.

Thank you so much for your help, sir! I don't quite understand the solution for question 2, why do we have to multiply it with 4? Could you explain?12/08/20