14) How many numbers are there between 100 and 1000 such that at least one of the digit is 5

First, let us find all numbers between 100 and 1000 which do not have digit 5 in any place. The number of such numbers is 8 x 9 x 9 = 648 (including 100). We have also seen in part (ii) that there are 900 numbers between 100 and 100 (including 100). Hence there are 900 -648 = 252 numbers between 100 and 1000 which have at least one digit as 5.