The GCD of given numbers is 11.
Step 1 : Find prime factorization of each number.
$$\begin{aligned}418 =& 2\cdot11\cdot19\\[8pt]253 =& 11\cdot23\\[8pt]\end{aligned}$$(view steps on how to factor 418 and 253. )
Step 2 : Put a box around factors that are common for all numbers:
$$\begin{aligned}418 =& 2\cdot\color{blue}{\boxed{11}}\cdot19\\[8pt]253 =& \color{blue}{\boxed{11}}\cdot23\\[8pt]\end{aligned}$$Step 3 : Multiply the boxed numbers together:
$$ GCD = 11 $$This solution can be visualized using a Venn diagram.
The GCD equals the product of the numbers at the intersection.