Question

determine the number of combinations of 7 out of 10 items. and then determine the number of combinations of 4 out of 7 items.

Answer 1

n!/(r!(n-r)!)

10! /(7! * 3!) = 10*9*8/(3*2)=10*3*4 = 120

7!/(4! * 3!) = 7*6*5/(3*2) =7*5 =35