Question

5. Which of the following numbers are co-prime?
i. 4,9
ii. 8, 15
iv. 40, 515
v. 73,213


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Answer 1

i. 4,9

Factors of 4 = 4, 2, 1

Factors of 9 = 3,9,1

ii. 8,15

Factors of 8 = 2,4,8,1

Factors of 15 = 3,5,15,1

iii. 73,213

Factors of 73 = 73,1

Factors of 213 = 3, 71, 213, 1

All these pairs have only 1 as their common factor which makes them co prime numbers.

While the pair iv. 40,515 has 5 as a common factor too, thus are not co prime numbers.

Hope that helps.