Which pair of numbers is relatively prime?

A. 12 and 35 B. 10 and 24 C. 18 and 33 D. 9 and 21

Definition: Two numbers that are relatively prime cannot be divided by the same number (except for 1)

Since, 10 & 24 can both be divided by 2, 18 & 33 can both be divided by 3, & 9 & 21 can both be divided by 3, by process of elimination, the correct answer is:

A) 12 & 35

12 can be divided by 1, 2, 3, 4, 6, & 12

35 can be divided by 1, 5, 7, & 35

the only common term is 1 and no others, so this supports the answer is A)