Question

Which of the following pairs is not co-prime?

• A. 99, 109
• B. 45, 36
• C. 20, 21
• D. 25, 22

Answer 1

The correct option is B 45, 36

Co-prime numbers are pairs of numbers that do not have any common factor other than 1. There should be a minimum of two numbers to form a set of co-prime numbers. Such numbers have 1 as their highest common factor.
In the above options, 45 and 36 have a common factor, 9, which means they are not co-prime.