Question

Use the lists of common factors to answer the question

FACTORS OF 9: 1,3,9


FACTORS OF 15: 1,3,5,15

FACTORS OF 21: 1,3,7,21

FACTORS OF 40: 1,2,4,5,10,20,40



Which pairs of numbers are relatively prime? check all that apply.

9 and 15

9 and 40

9 and 21

15 and 21

21 and 40​

Answer 1

9 and 40

21 and 40

Explanation:

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Factors of 9:

1,3,9

Factors of 15:

1,3,5,15

Factors of 21:

1,3,7,21

Factors of 40:

1,2,4,5,8,10,20,40

We have to find the pairs of numbers which are relatively prime.

Relatively prime number: The numbers in which gcd 1 are called relative prime numbers.

a.9 and 15

GCD(9,15)=3

9 and 15 are not relatively prime.

b.9 and 40

GCD(9,40)=1

Hence, 9 and 40 are relatively prime.

c.9 and 21

GCD(9,21)=3

9 and 21 are not relatively prime.

d.15 and 21

GCD(15,21)=3

15 and 21 are not relatively prime.

e.21 and 40

GCD(21,40)=1

21 and 40 are relatively prime.