100 through 999
There are 999 integers in this list
1,2,3,4,...99,100,101,102,103,...999
and if we take away the 99 that are only 1 or 2 digits
1,2,3,4,...99
we have 999-99 = 900
Answer = 900
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Or, if your teacher doesn't like that method,
we can choose the first digit any of 9 ways,
the second digit any of 10 ways, and the third
digit 10 ways. Then 9×10×10 = 900.
You can do it either way. Pick the way your
teacher prefers.
Edwin
