1.How many natural numbers less than 100 contain a 3? (Note that 13, 35 and 73 all contain a 3 but 42, 65 and 88 do not). What proportion is this?

2.Approximately what proportion of numbers less than 1000 contain a 3?

3.Explain why almost all million-digit numbers contain at least one 3.

P.S. I know that there are 19 numbers less than 100 that contain 3 but I found that by counting to 100. Then how do I find the proportions?