Question

Which of the following pairs of numbers are co-prime?
a)12,84
b)30,415
c)17,68
d)7,10

Answer 1

Answer:

d)7,10

as they do not have any common factors

Answer 2

7 and 10  are pairs of numbers which are co-prime

Co-Prime numbers :

• natural numbers which have only 1 as a common factor
• Natural numbers which do not have any prime factor common
• All distinct prime numbers are co-prime numbers
• HCF (Highest common factors) of co-prime numbers is 1

Step 1

Find the factors of each number in given pairs

12 = 2 x 2 x 3

84 = 2 x 2 x 3 x 7

Step 2 :

Compare the factors

Note that 12 and 84 have 2 and 3 as common factors

Hence these numbers are not co prime

Using The same procedure for other given options:

30 and 415 has   5 as common factor

Hence not co-prime

68 = 17 x 4  Hence 17 is common factor

Therefore,  17 , 68 are not co prime

7 and 10 does not have any common factor

Hence (7 , 10)  are pair of numbers which are co prime.

option d) 7,10 is correct