Question

How many 3 digits numbers are odd?

Answer 1

Total number of 3 digit numbers = 999 - 99 = 900
there are equal numbers of even and odds.

So number of odd numbers = 900/2 = 450

Answer 2

3 digit numbers are : 100, 101, 102, 103,  ......  996, 997, 998, 999
               =  (100, 101), (102, 103), (104, 105), ......(996, 997), (998, 999)

  The odd numbers and even numbers are equal in the 3 digit numbers.

Total number of 3 digit numbers =  999 - 100 +1 = 900

So number of odd numbers = number of even numbers = 900/2 = 450