Difference between revisions of "2017 AMC 10B Problems/Problem 1"
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Mary thought of a positive two-digit number. She multiplied it by <math>3</math> and added <math>11</math>. Then she switched the digits of the result, obtaining a number between <math>71</math> and <math>75</math>, inclusive. What was Mary's number? | Mary thought of a positive two-digit number. She multiplied it by <math>3</math> and added <math>11</math>. Then she switched the digits of the result, obtaining a number between <math>71</math> and <math>75</math>, inclusive. What was Mary's number? | ||
Revision as of 01:07, 16 February 2017
Problem
Mary thought of a positive two-digit number. She multiplied it by 
and added 
. Then she switched the digits of the result, obtaining a number between 
and 
, inclusive. What was Mary's number?
Solution
Just try out the answer choices. Multiplying 
by and then adding and reversing the digits gives you 
, which works, so the answer is 
See Also
| 2017 AMC 10B (Problems • Answer Key • Resources) | ||
| Preceded by - |
Followed by Problem 2 | |
| 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. 
