Find Greatest Common Divisor of 12, 24, 42 and 60, using prime factorization.

Step 1 : Find prime factorization of each number.

$$\begin{aligned}12 =& 2\cdot2\cdot3\\[8pt]24 =& 2\cdot2\cdot2\cdot3\\[8pt]42 =& 2\cdot3\cdot7\\[8pt]60 =& 2\cdot2\cdot3\cdot5\\[8pt]\end{aligned}$$

(view steps on how to factor 12, 24, 42 and 60. )

Step 2 : Put a box around factors that are common for all numbers:

$$\begin{aligned}12 =& \color{blue}{\boxed{2}}\cdot2\cdot\color{red}{\boxed{3}}\\[8pt]24 =& \color{blue}{\boxed{2}}\cdot2\cdot2\cdot\color{red}{\boxed{3}}\\[8pt]42 =& \color{blue}{\boxed{2}}\cdot\color{red}{\boxed{3}}\cdot7\\[8pt]60 =& \color{blue}{\boxed{2}}\cdot2\cdot\color{red}{\boxed{3}}\cdot5\\[8pt]\end{aligned}$$

Step 3 : Multiply the boxed numbers together:

$$ GCD = 2\cdot3 = 6 $$

GCD Calculator