Alberto is learning to write the numbers at school. Today the teacher has made them write all the numbers from one to 100.

**Do you know how many times you will have written the digit 3?**

#### Solution

In total he will have written **20 times** the number 3. Once for every ten except 2 times for 33: 3, 13, 23, 33, etc. which are 11 in total and 9 times more from 30 to 39, not counting again 33.