# What is the greatest common factor of 16 and 40?

##### 3 Answers

May 9, 2018

8

#### Explanation:

16 divided by 8 is 2.

40 divided by 8 is 5.

Neither of these can be reduced by any more common numbers, so therefore, 8 is your greatest common factor.

May 9, 2018

The GCF of 16 and 40 is 8.

#### Explanation:

Make a factor tree of each number:

1 - 16

2 - **8**

4 - 4

**8** -2

16 - 1

1 - 40

2 - 20

4 - 10

5 - **8**

**8** - 5

10 - 4

20 - 2

40 - 1

May 10, 2018

8

#### Explanation:

When doing GCF (Greatest Common Factor) questions, I like to do a prime factorization first:

For GCF, we want all the primes that are common to both our numbers. See that there are three 2's in both 16 and 40. We don't use the fourth 2 since only the 16 has that and we don't use the 5 because only the 40 has that. Therefore, the GCF is 8: