SOLUTION: A pair of dice is rolled three times. Find the probability that at least two sums are 7. I am trying to figure out if I should use combinations or not and how to consider that it

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Question 603486: A pair of dice is rolled three times. Find the probability that at least two sums are 7.
I am trying to figure out if I should use combinations or not and how to consider that it says at least.
Answer by scott8148(6628) About Me  (Show Source):
You can put this solution on YOUR website!
this is a binomial probability ___ either 7 or not 7

there are 6 ways to get 7 out of 36 possible outcomes ___ so the probability of 7 (on any roll) is 6/36 or 1/6
___ P(s) = 1/6 , P(n) = 5/6

the expansion is ___[P(s) + P(n)]^3 = s^3 + 3s^2n + 3sn^2 + n^3

at least two means the sum of the first two terms (with s^3 and s^2)

P = (1/6)^3 + [3 * (1/6)^2 * (5/6)]