# How do you find the greatest common factor of 40, 10?

Mar 4, 2018

$G C F \left(10 , 40\right) = 10$

#### Explanation:

list all the factors of each number, and pick out the common ones

factors of $10 : \left\{\textcolor{red}{1 , 2 , 5 , 10}\right\}$

factors of $40 : \left\{\textcolor{red}{1 , 2} , 4 , \textcolor{red}{5} , 8 , \textcolor{red}{10} , 20 , 40\right\}$

common factors $\left\{1 , 2 , 5 , 10\right\}$

$G C F \left(10 , 40\right) = 10$