Question

A father with 7 children takes 4 of them at a time to the zoo, as often as he can without taking the same four children together more than once. how often will each child go?

Answer 1

lets assume that here 7 children are : A,B,C,D,E,F,G.
If we target child A then he could go to zoo 20 times with his father .
Because here are 7 children and 4 place .
if we fix place one for child A then remaining 3 place for 6 children.
so simple maths formula
6c3 means =(6×5×4)/(3×2×1)
so the answer is 20 times A can go with his father.