If only the positive integers from 1 through 49, inclusive, are written on a piece of paper, how many times is the digit 1 written?

Guest Apr 16, 2021

#2**+1 **

We can start with cases

Case 1: How many of the one digit numbers have the digit 1? We easily know that there is only 1

Case 2: How many of the digit one is written from 10-19? We count that there are 10 digit ones in the first digit and one digit in the last digit. This gives us 11 digit 1 written.

Case 3: How many of the digit one is written from 20-49. There is only three which is 21, 31, and 41.

This gives us the total of **15** digit one written.

Hope this helped!

Mathdory Apr 16, 2021