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What is the probability of getting a sum of 22 or more when four dice are thrown?

Question: What is the probability of getting a sum of 22 or more when four dice are thrown?

(A) 5/432
(B) 5/523
(C) 5/652
(D) 5/325

Solution

Total number of ways = 64 = 1296. Number of ways of getting a sum 22 are 6,6,6,4 = 4! / 3! = 4
6,6,5,5 = 4! / 2!2! = 6. Number of ways of getting a sum 23 is 6,6,6,5 = 4! / 3! = 4.
Number of ways of getting a sum 24 is 6,6,6,6 = 1.
Fav. Number of cases = 4 + 6 + 4 + 1 = 15 ways. P (getting a sum of 22 or more) = 15/1296 = 5/432

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