CMAT 2020 Solved Question Paper

Let the required numbers be 9a and 9b
Then, 9a + 9b = 135
⇒ a + b = 15
Now, co-primes with sum 15 are
(1, 14), (2, 13), (4, 11), (7, 8)
∴ Required numbers are (9 × 1, 9 × 14), (9 × 2, 9 × 13), (9 × 4, 9 × 11) and (9 × 7, 9 × 8)
i.e., (9, 126), (18, 117), (36, 99) and (63, 72)
Hence, the number of such pairs is 4.