Question

Find the GCD of 18, 36 and 72 using Factor Tree.

Answer 1

Let's generate the Factor Tree of each number one by one.

$\underset{–}{18}$

$\underset{–}{36}$

$\underset{–}{72}$


$\to 18=2\times 3\times 3$
$\to 36=2\times 2\times 3\times 3$
$\to 72=2\times 2\times 2\times 3\times 3$

The common factors in all the three numbers are $2\&3^2.$
$\therefore$ GCD $=2\times 3\times 3=18$