Which of the following pairs of numbers are co-prime? Class 6

Which of the following pairs of numbers are co-prime? Class 6

Question 1.

Which of the following pairs of numbers are co-prime? Class 6

(a) 18 and 35

(b) 15 and 37

(c) 30 and 415

(d) 17 and 69

(e) 81 and 18

Solution:

(a) 18 and 35 are co-prime

(b) 15 and 37 are co-prime

(c) 30 and 415 are not co-prime, because they have common factor 5.

(d) 17 and 69 are co-prime

(e) 81 and 18 are not co-prime, because they have common factors 3 and 9.

Question 2.

While playing the ‘idli-vada' game with different number pairs, Anshu observed something interesting! Class 6

(a) Sometimes the first common multiple was the same as the product of the two numbers.

(b) At other times the first common multiple was less than the product of the two numbers.

Find examples for each of the above. How is it related to the number pair being co-prime?

Solution:

(a) First common multiple will be the product of two numbers, if the numbers are co-prime. For example, 2 and 5, 3 and 7, 5 and 9 and so on.

(b) First common multiple will be less than the product of two numbers, if the two numbers are not co-prime. For example, 4 and 6, 10 and 15, 7 and 14 and so on.