Question

From a group of 18 customers 5 are to be chosen to receive a special gift. Assuming that the order is in which the customers are children is irrelevant, how many group of 5 custom it can be chosen?

Answer 1

`k` objects can be chosen out of
`n` objects, when the order doesn't matter, in
`C(n,k)=(n!)/(k!(n-k)!)` ways.

So, the answer is
`C(18,5)=(18!)/(5!13!)=(14\cdot15\cdot16\cdot17\cdot18)/(2\cdot3\cdot4\cdot5)=8,568`