Question

Which pair of numbers is relatively prime?

A. 12 and 54

B. 9 and 21

C. 21 and 39

D. 15 and 49

Answer 1

The answer is D (15 and 49)

Answer 2

D. 15 and 49

Explanation:

Numbers are relatively prime if the only positive integer that divides both of them is 1.

A. 12 and 54

both 12 and 54 can be divided by 3

12/3 =4 54/3 = 18

B. 9 and 21

both 9 and 21 can be divided by 3

9/3 =3 and 21/3 = 7

C. 21 and 39

both 21 and 39 can be divided by 3

21/3 =7 and 39/3 = 13

D. 15 and 49

13 is 3*5 and 49 is 7*7

This is relatively prime