Question

What is the GCF of 42 and 18?

Answer 1

Break both numbers down to prime factors.

Explanation:

`42=2xx3xx7`
`18=2xx3xx3`

The primes they have in common are:
`2xx3=6`

Answer 2

`6`

Explanation:

One method of finding the GCF of two numbers goes as follows:

• Divide the larger number by the smaller to give a quotient and remainder.

• If the remainder is `0` then the smaller number is the GCF.

• Otherwise repeat with the smaller number and the remainder.

In our example we find:

`42/18 = 2" "` with remainder `6`

`18/6 = 3" "` with remainder `0`

So the GCF of `42` and `18` is `6`