Question

Two dice are rolled. What is the probability of getting a sum of 3 or 8?

Answer 1

To find the probability of getting a sum of 3 or 8:

It is given that,

Two dice are rolled.

So, the total sample space, n(s)=36.

A be the event of getting a sum of 3.

So, A={(1,2), (2,1)}

n(A)=2

B be the event of getting a sum of 8.

So, B={(2,6), (3,5), (4,4), (5,3), (6,2)}

n(B)=5.

n(AnB)=0.

Using the formula,

`\begin{gathered} P(A\cup B)=P(A)+P(B)-P(A\cap B) \\ =(n(A))/(n(S))+(n(A))/(n(S))-(n(A\cap B))/(n(S)) \\ =(2)/(36)+(5)/(36)-0 \\ =(7)/(36) \end{gathered}`

Hence, the answer is,

`(7)/(36)`