Question

Which of the following pairs represent ​
co-prime numbers?​

• A. (13,91)
• B. (17,29)
• C. (117,13)
• D. (12,84)

Answer 1

The correct option is B (17,29)

• Option A, (117,13)​

13 = 1 × 13 and 117 = 1 × 3 × 3 × 13 ​

(117, 13) have one common factor other than 1. It’s not a co-prime number.​

• Option B, (12,84) ​

12 = 1 × 2 × 2 × 3 and 84 = 1 × 2 × 2 × 3 × 7 ​

• (12, 84) have more than one common factor - 2, and 3. It’s not a co-prime number.​

• Option C, (17,29) ​

• 17 = 1 × 17 and 29 = 1 × 29​

(17, 29) have no common factor except 1. It’s a co-prime number.​

This is the correct answer.​

• Option D, (13,91)​

13 = 1 × 13 and 91 = 1 × 7 × 13> ​

(13, 91) have more than one common factor which is 13. ​

It’s not a co-prime number.​

Hence, option C is correct. ​