The GCD of given numbers is 1.
Step 1 :
Divide $ 40 $ by $ 9 $ and get the remainder
The remainder is positive ($ 4 > 0 $), so we will continue with division.
Step 2 :
Divide $ 9 $ by $ \color{blue}{ 4 } $ and get the remainder
The remainder is still positive ($ 1 > 0 $), so we will continue with division.
Step 3 :
Divide $ 4 $ by $ \color{blue}{ 1 } $ and get the remainder
The remainder is zero => GCD is the last divisor $ \color{blue}{ \boxed { 1 }} $.
We can summarize an algorithm into a following table.
40 | : | 9 | = | 4 | remainder ( 4 ) | ||||
9 | : | 4 | = | 2 | remainder ( 1 ) | ||||
4 | : | 1 | = | 4 | remainder ( 0 ) | ||||
GCD = 1 |
This solution can be visualized using a Venn diagram.
The GCD equals the product of the numbers at the intersection.