Question

Mr. lewis is going on a trip. he has 11 books that he hasn't read yet, but he wants to bring only 2 on the trip. in how many ways can he choose 2 books to bring on the trip?

Answer 1

In this problem, we will use the combination formula. Combination is where the order of the things doesn’t matter.

So the formula for this problem is:

n! divided by r! (n-r)! = n/r

where:

n is the number of things to choose from and we choose r of them

11C2 = 11! / [2! (11 - 2)!]
= 11! / (2! * 9!)
= 55