Step 1 :
Divide $ 340 $ by $ 195 $ and get the remainder

$$ 340 : 195 = 1 \text{ ( remainder is } \color{blue}{ 145 } \text{ ) } $$

The remainder is positive ($ 145 > 0 $), so we will continue with division.

Step 2 :
Divide $ 195 $ by $ \color{blue}{ 145 } $ and get the remainder

$$ 195 : 145 = 1 \text{ ( remainder is } \color{blue}{ 50 } \text{ ) } $$

The remainder is still positive ($ 50 > 0 $), so we will continue with division.

Step 3 :
Divide $ 145 $ by $ \color{blue}{ 50 } $ and get the remainder

$$ 145 : 50 = 2 \text{ ( remainder is } \color{blue}{ 45 } \text{ ) } $$

The remainder is still positive ($ 45 > 0 $), so we will continue with division.

Step 4 :
Divide $ 50 $ by $ \color{blue}{ 45 } $ and get the remainder

$$ 50 : 45 = 1 \text{ ( remainder is } \color{blue}{ 5 } \text{ ) } $$

The remainder is still positive ($ 5 > 0 $), so we will continue with division.

Step 5 :
Divide $ 45 $ by $ \color{blue}{ 5 } $ and get the remainder

$$ 45 : \color{blue}{ \boxed { 5 }} = 9 \text{ ( remainder is } \color{blue}{ 0 } \text{ ) } $$

The remainder is zero => GCD is the last divisor $ \color{blue}{ \boxed { 5 }} $.

This solution can be visualized using a Venn diagram.

The GCD equals the product of the numbers at the intersection.

GCD Calculator