Question

Which of the following statements is true about $63$ and $20$?

• A. They are relatively prime.
• B. They have more than one common factor.
• C. They each have a factor of $4$.
• D. They are both prime numbers

Answer 1

The correct option is A

They are relatively prime.

Explanation for the correct options:

What is a relatively prime number?

Two integers a and b are coprime, relatively prime or mutually prime if the only positive integer that is a divisor of both of them is $1.$

$20$ and $63$ have no common factor greater than $1.$

Factors of $63:1,3,7,9,21,63$

Factors of $20:1,2,4,5,10,20$

Therefore, $20$ and $63$ are relatively prime.

Hence, the correct answer is option (A).