Which pair of numbers is relatively prime?

10 and 21

12 and 54

15 and 27

21 and 39

Question

Which pair of numbers is relatively prime?
 
       10 and 21

        12 and 54

        15 and 27

        21 and 39

loser66 · Answer

definition of relatively prime?

anonymous · Answer

No which pair are relatively prime.

loser66 · Answer

I know, but to solve it, you have to know the definition of relative prime, What is it?

anonymous · Answer

I don't know, that's why I am asking

anonymous · Answer

10 and 21 - between them, they have no common prime factors.

anonymous · Answer

I'm just going out on a limb here, but would it be 10 and 21?

I guess that because that is the only pair that does not have any common denominators. The other three pairs are divisible by three while 10 is not, making 10 and 21 the odd pair.

anonymous · Answer

Ok thank you