Permutations of r items from n different items

In this tutorial I show you how to calculate how many arrangements of r items taken from n items. I introduce the formula nPr and show you it on a calculator.
You are also given this question
7 people get into a train but only 4 seats are available. How many different ways are of there of seating 4 people?

2016-09-07T21:42:20+00:00