Question

Which of the following are pairs of coprimes? 

i. 8,14 

ii. 4,5 

iii. 17,19 

iv. 27,15

Answer 1

i. 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.

ii. 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.

iii. 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

iv. 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.