Solution: Numbers with H.C.F. 15 must contain 15 as a factor.
Now, multiples of 15 between 35 and 95 are 45, 60, 75, 90.
.'. Number pairs with H.C.F. 15 are (45, 60), (45, 75), (60, 75), (75, 90). ['.' H.C.F. of(60, 90) is 30 and that of (45, 90) is 45]
Hence clearly, there are 4 such pairs.