2021 Fall AMC 10A Problems/Problem 9
Contents
Problem
When a certain unfair die is rolled, an even number is 
times as likely to appear as an odd number. The die is rolled twice. What is the probability that the sum of the numbers rolled is even?
Solution
Since an even number is times more likely to appear than an odd number, the probability of an even number appearing is 
. Since the problem states that the sum of the two die must be even, the numbers must both be even or both be odd. We either have EE or OO, so we have ![\[\frac{3}{4}\cdot \frac{3}{4} + \frac{1}{4} \cdot \frac{1}{4} = \frac {1}{16} + \frac {9}{16} = \frac{10}{16} = \boxed{\textbf{(E)}\ \frac{5}{8}}.\]](http://latex.artofproblemsolving.com/a/9/d/a9df2f4f8f0bd33c690522e4a4abce345ead2579.png)
~Arcticturn ~Aidensharp
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Video Solution by TheBeautyofMath
https://youtu.be/ycRZHCOKTVk?t=661
~IceMatrix
Video Solution by WhyMath
https://youtu.be/oOKx2Wqp_ig ~savannahsolver
See Also
| 2021 Fall AMC 10A (Problems • Answer Key • Resources) | ||
| Preceded by Problem 8 |
Followed by Problem 10 | |
| 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. 
