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prealgebra intermediate

Problem

How many different 7-digit positive integers exist? (Note that we don't allow "7-digit" integers that start with 0, such as 0123456; this is actually a 6-digit integer.)
Solution
There are 9 choices for the first digit (it can be 1-9) and 10 choices for each of the other 6 digits (they can be 0-9). So there are possible numbers.
Final answer
9,\!000,\!000