Find the GCF of the given numbers. See Example 7. 9, 12 Reference Example 7. Find...

Find the GCF of the given numbers. See Example 7.

9, 12

Reference Example 7.

Find the GCF of 18 and 45.

Strategy We will find the factors of 18 and 45.

Why Then we can identify the largest factor that 18 and 45 have in common.

Solution

To find the factors of 18, we find all the pairs of whole numbers whose product is 18. There are three possibilities:

1 . 18 = 18 2 . 9 = 18 3 . 6 = 18

To find the factors of 45, we find all the pairs of whole numbers whose product is 45. There are three possibilities:

1 . 45 = 45 3 . 15 = 45 5 . 9 = 45

The factors of 18 and 45 are listed below. Their common factors are circled.

The common factors of 18 and 45 are 1, 3, and 9. Since 9 is their largest common factor,

GCF (18, 45) = 9 Read as “The greatest common factor of 18 and 45 is 9.”