Greatest Common Factor of 3 Numbers

Given three numbers, the method of finding greatest common factor is same as the method of finding gcf of two numbers.

• We list all the factors of the three numbers.
• We look for the common factors of these numbers.
• Among these we find for the greatest number which will be the gcf of the three given numbers.

Find the greatest common factor of 18, 24 and 36

Solution

Step 1:

The factors of 18 and 24 and 36 are

18 = 1, 2, 3, 6, 9, 18

24 = 1, 2, 3, 4, 6, 8, 12, 24

36 = 1, 2, 3, 4, 6, 9, 12, 18, 36

Step 2:

The common factors of 18, 24 and 36 are shown in bold.

Step 3:

The greatest among these is 6. So the greatest common factor (gcf) of 18, 24 and 36 is 6.

Find the greatest common factor of 15, 35 and 75

Solution

Step 1:

The factors of 15, 35 and 75 are

15 = 1, 3, 5, 15

35 = 1, 5, 7, 35

75 = 1, 3, 5, 15, 25, 75

Step 2:

The common factors of 15, 35 and 75 are shown in bold.

Step 3:

The greatest among these is 5. So the greatest common factor (gcf) of 15, 35 and 75 is 5.