Question

A book has 100 pages, How many times is the digit ''3'' used numbering its pages?

Answer 1

19 pages. 3,13,23,30,31,32,33,34,35,36,37,38,39,43,53,63,73,83,93

Answer 2

18 pages
Because if each 10 pages consists 1 page with number 3 (3, 13, 23 and etc.)
We have 10 pages with no. 3.
Also there is 30 - 39 numbers
Excluding 33 there is 8 of that kind of pages
10 + 8 = 18