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Mahowny rolls two fair, six-sided dice. You don't know what the rolls were, but you are told that the sum of the two rolls is a prime. What is the probability that the sum of the two rolls is 5?

 Feb 5, 2020
 #1
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The following outcomes  are  prime

 

2, 3, 5, 7, 11

 

Ways to roll    2    =  1

Ways to roll  3    =   2

Ways to roll  5  =  4

Ways to roll  7  =  6

Ways to roll 11 =  2

 

 

P ( 5  given that the outcome is a prime)  =

 

           4                                  4

______________  =            _____

1 + 2 + 4 + 6 + 2                   15

 

 

cool cool cool

 Feb 5, 2020

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