2009 AMC 10A Problems/Problem 5
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Problem
What is the sum of the digits of the square of 111,111,111 ?
Solution
Using the standard multiplication algorithm, 
whose digit sum is 
Or
Add up all the ones(thus deriving the sum of the number) of 
gives us 
Thus, 
See also
| 2009 AMC 10A (Problems • Resources) | ||
| Preceded by Problem 4 | Followed by Problem 6 | |
| 1 • 2 • 3 • 4 • 5 • 6 • 7 • 8 • 9 • 10 • 11 • 12 • 13 • 14 • 15 • 16 • 17 • 18 • 19 • 20 • 21 • 22 • 23 • 24 • 25 | ||
