Question

How many times will the digit '1' appear if we write all whole numbers from 1 to 99?

Answer 1

19

Explanation:

From 1 to 9, there is one 1.

From 10 to 19, there are ten 1s.

From 20 to 29, there is one 1.

From 30 to 39, there is one 1.

Repeating all the way to 90 to 99, there are eight 1s between 20 and 99.

So the total number of 1s is 1 + 10 + 8 = 19.