Question

Find the GCF (21,15,45)

Answer 1

We are asked to find the Greatest Common Factor of the following numbers:

$21\text{ 15 45}$

To do that we need to find the factors of each number, that is the number that gives a residue of zero when divided by them

For 21 the factors are:

$1,\text{ 3, 7, 21}$

For 15 the factors are:

$1,\text{ 3, 5, 15}$

For 45 the factors are:

$1,3,5,9,15,45$

The GCF is the factor that is repeated in each number, that is 3. Therefore:

$\text{GCF}(21,15,45)=3$