Question

Which pair of numbers is relatively prime

A. 57 and 96
B. 68 and 118
C. 70 and 195
D. 143 and 323

Answer 1

D is correct.

Explanation:

I just finished taking the quiz.

Answer 2

Without any calculations it's evident it can't be neither B (both numbers are even, so they're divisible by 2) nor C (the numbers end in 0 and 5, so they're divisible by 5).

A.

`57=3\cdot19\\ 96=2^5\cdot3`
Both numbers have a factor of 3, so they're not relatively prime.
That means it must be D. But, let's check it.


`143=11\cdot13\\ 323=17\cdot19`

Indeed, those two numbers are relatively prime.