# How do you find the GCF of 9 and 15 and 24?

##### 1 Answer

#### Answer:

GCF = 3

#### Explanation:

A factor is a number that when multiplied by another number, gives us the number in question. So for instance 3 is a factor of 9 because

The GCF is the highest number that is a factor of all three of our "test subject numbers".

So let's do a prime factorization of all three to start things out and I'll colour the different prime values in different colours:

Ok, now let's find what is common.

**2**

There are 2s in 24 but not in 9 or 15, so there are no 2s in our GCF.

**3**

There is one 3 in 24 and in 15 and two in 9 - so one 3 is common to all three numbers.

**5**

There is a 5 in 15 but not in 9 or 24, so the GCF doesn't have a 5.

And there are no more prime numbers.

This means our GCF = 3.