The seventh book in the Harry Potter series has 759 pages. How many 2s were used when typing the page numbers?
From 0 to 99, there are 2*10=20 2's.
from 100 to 199, there are 20 2's.
...
from 600 to 699, there are 20 2's.
From 700 to 759, there are 20-4 2's.
How many 2's are there in all?