How many combinations are there?

Question

Amy, Ben, Charles, and Don all called into a radio show to get free tickets to a concert. Find out how many different orders there are and list all the possible orders in which their calls could have been received.

Answer 1

There are 4 choices for the first to be called, 3 for the second, 2 got the third, and 1 for the fourth

 

The possible orders is 4x 3 x 2 x 1 = 24