posted by MATH Help .
How many counting numbers between 100 and 1000 have at least one 2 as a digit?
There are 900 of those counting numbers with no restriction.
Let's find all those that DON'T have a 2 in them
there are 8 possible in the left spot , (no 2 or 0)
but 9 anywhere else
number of counting numbers with NO 2 in them is
8x9x9 = 648
So 900 - 648 or 252 of them have at least one 2 in them.