Here, the HCF = 33 Then, let the two numbers be 33a and 33b respectively Where a and b are coprime. Then, 33a+33b=528 ⇒a+b=16 Hence, values of (a, b) which are coprime to each other can be (1, 15), (3, 13), (5, 11) and (7, 9) Hence, required number of pairs is 4.