Difference between revisions of "1992 USAMO Problems/Problem 1"
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Latest revision as of 17:52, 27 April 2017
Problem
Find, as a function of the sum of the digits of where each factor has twice as many digits as the previous one.
Solution
The answer is .
Let us denote the quantity as . We wish to find the sum of the digits of .
We first note that so is a number of at most digits. We also note that the units digit is not equal to zero. We may thus represent as where the are digits and . Then Thus the digits of are and the sum of these is evidently , as desired.
Alternate solutions are always welcome. If you have a different, elegant solution to this problem, please add it to this page.
See Also
1992 USAMO (Problems • Resources) | ||
First Problem | Followed by Problem 2 | |
1 • 2 • 3 • 4 • 5 | ||
All USAMO Problems and Solutions |
The problems on this page are copyrighted by the Mathematical Association of America's American Mathematics Competitions.