Difference between revisions of "2011 AMC 8 Problems/Problem 22"
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What is the tens digit of <math>7^{2011}</math>? | What is the tens digit of <math>7^{2011}</math>? | ||
Revision as of 18:14, 4 November 2012
Problem
What is the tens digit of 
?
Solution
The first couple powers of 
are 
As you can see, the last two digits cycle after every 4 powers. 
From there, we go two more powers. The last two digits are 
so the tens digit is 
See Also
| 2011 AMC 8 (Problems • Answer Key • Resources) | ||
| Preceded by Problem 21 |
Followed by Problem 23 | |
| 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 AJHSME/AMC 8 Problems and Solutions | ||
