Find the probability distribution of Y in two throws of two dice, where Y represents the number of times a total of 9 appears.

When two fair dice are thrown there are total 36 possible outcomes.


In our question, we are throwing two dice 2 times


Y denotes the number of times, a sum of two numbers appearing on dice is equal to 9.


Y can take values 0,1 or 2


Means In both the throw sum of 9 is not obtained, in one of throw of two dice 9 is obtained and in both the throws of two dice a sum of 9 is obtained.


(3,6) (6,3) (5,4) and (4,5) are the combinations resulting in sum = 9


Let A denotes the event of getting a sum of 9 in a throw of 2 dice


P(A) = probability of getting the sum of 9 in a throw of 2 dice is


And P(A’) = probability of not getting the sum of 9 in the throw of 2 dice =


Note: P(AՈB) = P(A)P(B) where A and B are independent events.


P(Y = 0) = P(A’)×P(A’) =


P(Y = 1) = P(A)×P(A’)+ P(A’)×P(A)+ =


P(Y = 2) = P(A)×P(A) =


Now we have pi and xi.


The required probability distribution is:-



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