Question
Find Greatest Common Divisor of 391 and 667, using prime factorization.
Answer
The GCD of given numbers is 23.
Explanation
Step 1 : Find prime factorization of each number.
$$\begin{aligned}391 =& 17\cdot23\\[8pt]667 =& 23\cdot29\\[8pt]\end{aligned}$$(view steps on how to factor 391 and 667. )
Step 2 : Put a box around factors that are common for all numbers:
$$\begin{aligned}391 =& 17\cdot\color{blue}{\boxed{23}}\\[8pt]667 =& \color{blue}{\boxed{23}}\cdot29\\[8pt]\end{aligned}$$Step 3 : Multiply the boxed numbers together:
$$ GCD = 23 $$This solution can be visualized using a Venn diagram.
The GCD equals the product of the numbers at the intersection.
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