Question

Which of the following are pairs of co-primes?

विकल्प

• 8, 14

• 4, 5

• 17, 19

• 27, 15

Answer 1

4, 5 and 17, 19

Explanation:

(1) Factors of 8: 1, 2, 4, 8

Factors of 14: 1, 2, 7, 14

∴ Common factors of 8 and 14: 1, 2

∴ 8 and 14 are not a pair of co-prime numbers.

(2) Factors of 4: 1, 4

Factors of 5: 1, 5

∴ Common factors of 4 and 5: 1

∴ 4 and 5 are a pair of co-prime numbers.

(3) Factors of 17: 1, 17

Factors of 19: 1, 19

∴ Common factors of 17 and 19: 1

∴ 17 and 19 are a pair of co-prime numbers.

(4) Factors of 27: 1, 3, 9, 27

Factors of 15: 1, 3, 5, 15

∴ Common factors of 27 and 15: 1, 3

∴ 27 and 15 are not a pair of co-prime numbers.