The GCD of given numbers is 4.
Step 1 :
Divide $ 24 $ by $ 20 $ and get the remainder
The remainder is positive ($ 4 > 0 $), so we will continue with division.
Step 2 :
Divide $ 20 $ by $ \color{blue}{ 4 } $ and get the remainder
The remainder is zero => GCD is the last divisor $ \color{blue}{ \boxed { 4 }} $.
We can summarize an algorithm into a following table.
24 | : | 20 | = | 1 | remainder ( 4 ) | ||
20 | : | 4 | = | 5 | remainder ( 0 ) | ||
GCD = 4 |
This solution can be visualized using a Venn diagram.
The GCD equals the product of the numbers at the intersection.