Difference between revisions of "2009 AMC 10A Problems/Problem 5"
| Line 12: | Line 12: | ||
==See also== | ==See also== | ||
{{AMC10 box|year=2009|ab=A|num-b=4|num-a=6}} | {{AMC10 box|year=2009|ab=A|num-b=4|num-a=6}} | ||
| + | {{MAA Notice}} | ||
Revision as of 10:55, 4 July 2013
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 • Answer Key • 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 | ||
| All AMC 10 Problems and Solutions | ||
The problems on this page are copyrighted by the Mathematical Association of America's American Mathematics Competitions. 
