Question

Number of different natural numbers which are smaller than two hundred million

Answer 1

These numbers will be either 1 digit,2 digits,.......9 digits.Number of such 9 digits numbers are 28,number of such 8 digits numbers are 28 and so on.So the total numbers are 28+28+27+26+.........+22+21.

But the answer is 3×28−2

Answer 2

Number of different natural numbers which are smaller than two hundred million would be 199,999,999

The natural numbers that are smaller than two hundred million are the natural numbers that lie in the set of natural numbers upto two hundred million i.e.{1,2,3,4, .......... , 2 hundred million}

Since 2 hundred million can be written as 200,000,000

The number of natural numbers less than that would be 199,999,999