Step 1 :
Divide $ 2025 $ by $ 1955 $ and get the remainder

$$ 2025 : 1955 = 1 \text{ ( remainder is } \color{blue}{ 70 } \text{ ) } $$

The remainder is positive ($ 70 > 0 $), so we will continue with division.

Step 2 :
Divide $ 1955 $ by $ \color{blue}{ 70 } $ and get the remainder

$$ 1955 : 70 = 27 \text{ ( remainder is } \color{blue}{ 65 } \text{ ) } $$

The remainder is still positive ($ 65 > 0 $), so we will continue with division.

Step 3 :
Divide $ 70 $ by $ \color{blue}{ 65 } $ and get the remainder

$$ 70 : 65 = 1 \text{ ( remainder is } \color{blue}{ 5 } \text{ ) } $$

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

Step 4 :
Divide $ 65 $ by $ \color{blue}{ 5 } $ and get the remainder

$$ 65 : \color{blue}{ \boxed { 5 }} = 13 \text{ ( remainder is } \color{blue}{ 0 } \text{ ) } $$

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