The GCD of given numbers is 32.
Step 1 :
Divide $ 640 $ by $ 32 $ and get the remainder
The remainder is zero => GCD is the last divisor $ \color{blue}{ \boxed { 32 }} $.
We can summarize an algorithm into a following table.
640 | : | 32 | = | 20 | remainder ( 0 ) |
GCD = 32 |
This solution can be visualized using a Venn diagram.
The GCD equals the product of the numbers at the intersection.