LCM and HCF Practice Test 3

Let the two numbers be 33x and 33y.
Then, 33x + 33y = 528
⇒ 33 (x + y) = 528
⇒ (x + y) = 16
Now, the co-primes with sum 16 are (1, 15), (3, 13), (5, 11) and (7, 9)
Hence, the number of such pairs = 4.