Question

How many ways can an IRS auditor select 5 of 12 tax returns for an audit?

Answer 1

792

Explanation:

The number of ways that k things can be chosen from a collection of n things is given by ...

nCk = n!/(k!(n-k)!)

Here, we want the number of ways 5 items can be chosen from 12. That is ...

12C5 = 12!/(5!·7!) = 12·11·10·9·8/(5·4·3·2·1) = 11·9·8

12C5 = 792

There are 792 ways 5 returns can be chosen from 12.