Question

Which pair of numbers is relatively prime?

7 and 21
4 and 15
6 and 9
9 and 27

Answer 1

(B)4 and 15

Explanation:

(A) The given numbers are:

7 and 21

Factorization of 7=7×1 and Factorization of 21=3×7.

Since, 3 is the common factor in Factorization of both the numbers, therefore they are not prime numbers.

(B) The given numbers are:

4 and 15

Factorization of 4=1×4 and Factorization of 15=1×15, since in the Factorization of both the numbers, there is no common number than one, thus 4 and 15 are prime numbers.

(C) The given numbers are:

6 and 9

Factorization of 6=2×3 and Factorization of 9=3×3,

Since, 3 is the common factor in Factorization of both the numbers, therefore they are not prime numbers.

(D)The given numbers are:

9 and 27

Factorization of 9=3×3 and Factorization of 27=3×3×3,

Since, 3 is the common factor in Factorization of both the numbers, therefore they are not prime numbers.

Answer 2

4 = 2² and 15 = 3·5 have no prime factors in common. The pair that is relatively prime is ...
4 and 15