POTW75 Solution

Answer to POTW75 is A) 0.

1 \cdots 9 takes up 9 digits
10\ 11 \cdots 99 takes up 180 digits
100\ 101 \cdots 199 takes up 300 digits

So the last digit of 699 is actually the 9+180+1800 = 1989th digit.
It is easy to list the remaining
700\ 701 \ 702 \ 703 \ 70

And so the answer is 0.

By PC Toh, on December 7, 2012 at 9:37 am, under POTW Solutions. No Comments
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