Question

Which pair of numbers is relatively prime?

Answer 1

Answer:

a

Step-by-step explanation:

Just took quiz

Answer 2

Relatively prime means having no factors in common.

I will start by checking if they have the factor "3" in common: it's easy to check: the sum of its digit needs to be divisible by 3:

a. 72 And 115

7+2=9
1+1+5=7

not true that both are divisible by 3
b. 120 And 835
1+2=3
8+3+5=16


not true that both are divisible by 3
but, they're both divisible by 5! (0 or 5 at the end)
not relatively prime


 c. 201 And 735

2+1=3
7+3+5=15

both are divisible by 3!


d. 303 And 1041

3+3=6
1+4+1=6

both divisible by 3

the answer is a)