Wu rolls two fair, six-sided dice. You are not told 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

LuckyDucky May 2, 2020

#1**0 **

The possible rolls are (1,4), (2,3), (3,2), (4,1), so the probability is 4/36 = 1/9.

Guest May 2, 2020

#3**0 **

The sum could be either a 3, a 5, a 7, or an 11.

3 = (1,2) or (2,1)

5 = (1,4), (4,1), (2,3) or (3,2)

7 = (1,6), (6,1), (2,5), (5,2), (3,4), or (4,3)

11 = (5,6) or (6,5)

There are 14 winning possibilities out of a possible 36 possibilities: 14/36 = 7/18

geno3141 May 2, 2020

#5**+2 **

Hi LuckyDucky!

I'm probably wrong too, but I'll give this problem a shot too :)

So I basically did the same thing as the Guest who answered your question, but I think the answer is actually \(\boxed{\frac{4}{15}}\)because the questions says **"you are told that the sum of the two rolls is a prime" ** the answer is actually **4** out of the prime sums, and there are **15** possible prime sums. (The Guest made the mistake of making it out of all 36 possible sums)

So, I think the answer is \(\boxed{\frac{4}{15}}\)

I'm probably wrong, but I hope this helped you anyway

:)

lokiisnotdead May 2, 2020