Question

The greatest common divisor of $7,9$ and $21$ is

• A. $3$
• B. $1$
• C. $7$
• D. $0$

Answer 1

The correct option is B $1$


Prime factorization of $7,9$ and $21$ :
$7=1\times 7$
$9=1\times 3\times 3$
$21=1\times 3\times 7$
So, the GCD of $7,9$ and $21$ is $1.$