Finding the Greatest Common Divisor of Two Numbers by Factoring

number 1

200

number 2

20


2 × 2 × 2 × 5 × 5	2 × 2 × 5

the common factors of200and20are

2

,

2

,

5

gcd(200, 20) =

2

×

2

×

5

=20

You can find the greatest common divisor (GCD) of two numbers by multiplying together all the prime factors they have in common.