Step 1 :
Divide $ 2520 $ by $ 154 $ and get the remainder

$$ 2520 : 154 = 16 \text{ ( remainder is } \color{blue}{ 56 } \text{ ) } $$

The remainder is positive ($ 56 > 0 $), so we will continue with division.

Step 2 :
Divide $ 154 $ by $ \color{blue}{ 56 } $ and get the remainder

$$ 154 : 56 = 2 \text{ ( remainder is } \color{blue}{ 42 } \text{ ) } $$

The remainder is still positive ($ 42 > 0 $), so we will continue with division.

Step 3 :
Divide $ 56 $ by $ \color{blue}{ 42 } $ and get the remainder

$$ 56 : 42 = 1 \text{ ( remainder is } \color{blue}{ 14 } \text{ ) } $$

The remainder is still positive ($ 14 > 0 $), so we will continue with division.

Step 4 :
Divide $ 42 $ by $ \color{blue}{ 14 } $ and get the remainder

$$ 42 : \color{blue}{ \boxed { 14 }} = 3 \text{ ( remainder is } \color{blue}{ 0 } \text{ ) } $$

The remainder is zero => GCD is the last divisor $ \color{blue}{ \boxed { 14 }} $.

This solution can be visualized using a Venn diagram.

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

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