# How do you find the GCF of 10ab, 25a?

Aug 11, 2017

$5 a$

#### Explanation:

To find the GCF, look for the factor that both terms have in common
This one is $5 a$

Aug 11, 2017

$H C F = 5 a$

#### Explanation:

Write each term as the product of its prime factors:
Identify which factors are common to both

$\text{ } 10 a b = 2 \times \textcolor{b l u e}{5} \textcolor{w h i t e}{\times x} \times \textcolor{b l u e}{a} \times b$
$\text{ } 25 a = \underline{\textcolor{w h i t e}{\times . x} \textcolor{b l u e}{5} \times 5 \times \textcolor{b l u e}{a}}$
$H C F = \textcolor{w h i t e}{\times \times x} \textcolor{b l u e}{5} \textcolor{w h i t e}{\times x} \times \textcolor{b l u e}{a} = 5 a$

This method is very useful if you are working with several numbers, especially of they are large and unfamiliar.