Question

John is going to adopt

puppies from the pet store.
There are 13 puppies at the
store. How many ways can
he pick 3?

Answer 1

286

Explanation:

Let's say the puppies are named A, B, C, ..., L, M.

If he chooses A, B, L or A, L, B, he is picking the same group of three puppies.

In this case, the order does not matter.

This is a problem of combination, not permutation.

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

Here, n = 13; k = 3.

`=`

`= (13!)/(10!3!)`

`= (13 * 12 * 11)/(3 * 2 * 1)`

`= 286`

Answer: 286