2006 Alabama ARML TST Problems/Problem 11

Problem

The integer has 1403 digits, and 1 is its first digit (farthest to the left). For how many integers does begin with the digit 1?

Solution

Now either starts with 1, or has one more digit than . From to , we have 1402 changes (since 1 increases 1402 times to become 1403 after ), so those must not begin with the digit 1.

See also

2006 Alabama ARML TST (Problems)
Preceded by: Problem 10	Followed by: Problem 12
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