Question

From the numbers 2, 3, 4, 5, 6, 7, 8, 9 how many pairs of co-primes can be formed?
(a) 19
(b) 18
(c) 20
(d) 21

Answer 1

We can form 19 pairs of co primes from the 2, 3, 4, 5, 6, 7, 8, 9 which are given below,
(2, 3), (2, 5), (2, 7), (2, 9), (3, 4),(3, 5), (3, 7), (3, 8), (4, 5), (4, 7), (4, 9), (5, 6), (5, 7), (5, 8), (5, 9), (6, 7), (7, 8), (7, 9) and (8, 9)
Hence, the correct answer is option (a).