Question

Which pair of numbers is relatively prime?

A.
21 and 39

B.
10 and 21

C.
12 and 54

D.
15 and 27

Answer 1

HI!!

Answer 2

do you know what "relatively prime" means ?

Answer 3

no

Answer 4

then you can't do it

Answer 5

you need to know what it means before you can answer the question
https://www.mathsisfun.com/definitions/relatively-prime.html

Answer 6

@iGreen.

Answer 7

@iambatman

Answer 8

"Two integers are relatively prime if they share no common positive factors."

Answer 9

21 and 39

2 + 1 = ?
3 + 9 = ?

Answer 10

3
12

Answer 11

Yes, and both of those are divisible by 3, so A is not correct.

Answer 12

iGreen always beats me to it :), go igreen!

Answer 13

10 and 21

1 + 0 = ?
2 + 1 = ?

Answer 14

Thanks :)

Answer 15

1
3

Answer 16

Oh, and FYI, all of these are divisible by 3 except 1 pair, so we just have to find the 1 pair that isn't divisible by 3.

Answer 17

Okay, are both those numbers divisible by 3?

Answer 18

no

Answer 19

Yes, so B is our answer.

Answer 20

thnx @iGreen.