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

8

Explanation:

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

16=2xx2xx2xx2
40=2xx2xx2xx5

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:

8xx5=40
8xx2=16