What is the greatest common factor of 30 and 72?

Answer 1

The greatest common factor of the numbers 30 and 72 is 6.

Factors of 72: 1 2 3 4 6 8 9 12 18 24 36 72

Factors of 30: 1 2 3 5 6 10 15 30

The GCF of 72 and 30 is 6
One method would be to write down the factors of the lower number 30:

1,30,2,15,3,10,5,6.

Put them in descending order:

30,15,10,6,5,3,2,1.

Then starting from the left ask, "does this number divide into the higher number (72) a whole number of times?"

30 doesn't, 15 doesn't, 10 doesn't, 6 does!

So 6 is the highest common factor.

(Note: 6 goes into 72 twelve times and into 30 five times).
The factors of 30 are:

1, 2, 3, 5, 6, 10, 15, 30

The factors of 72 are:

1, 2, 3, 4, 6, 8, 9, 12, 18, 24, 36, 72

The common factors are:

1, 2, 3, 6

The Greatest Common Factor (GCF) is:

6

Answer 2

GCF(72, 30) = 6.

Answer 3

6