The GCD of given numbers is 30.
Step 1 : Find prime factorization of each number.
$$\begin{aligned}330 =& 2\cdot3\cdot5\cdot11\\[8pt]1140 =& 2\cdot2\cdot3\cdot5\cdot19\\[8pt]\end{aligned}$$(view steps on how to factor 330 and 1140. )
Step 2 : Put a box around factors that are common for all numbers:
$$\begin{aligned}330 =& \color{blue}{\boxed{2}}\cdot\color{red}{\boxed{3}}\cdot\color{Fuchsia}{\boxed{5}}\cdot11\\[8pt]1140 =& \color{blue}{\boxed{2}}\cdot2\cdot\color{red}{\boxed{3}}\cdot\color{Fuchsia}{\boxed{5}}\cdot19\\[8pt]\end{aligned}$$Step 3 : Multiply the boxed numbers together:
$$ GCD = 2\cdot3\cdot5 = 30 $$This solution can be visualized using a Venn diagram.
The GCD equals the product of the numbers at the intersection.