# Thread: probability of conditional events

1. ## probability of conditional events

can someone show me how to do second part and third part please?
i really have no idea how to start it.

2. ## Re: probability of conditional events

Originally Posted by delso
can someone show me how to do second part and third part please?
i really have no idea how to start it.
There are two problems with your question

First, part 2 and part 3 are invisible in your image. In fact, not even all your answers to part 1 are visible.

Second, even for part 1 you show no work, just answers. It is impossible for us to know what you are thinking when you just show answers.

3. ## Re: probability of conditional events

Write out all triples that sum to 5:

(1,1,3), (1,3,1), (3,1,1)
(1,2,2), (2,1,2), (2,2,1)

There are no other triples that sum to 5. How many triples are possible? There are six possible rolls for each die. So, there are $\displaystyle 6^3$ possible triples. Hence, $\displaystyle P(T) = \dfrac{6}{6^3} = \dfrac{1}{36}$. Then, $\displaystyle P(J|T)$ is the number of outcomes (among the six triples whose sum is five) that have a one in the third position. I count three. So, $\displaystyle P(J|T) = \dfrac{3}{6} = \dfrac{1}{2}$.

4. ## Re: probability of conditional events

sorry. i mean i manaed to get the ans for P(G2 n R3) only, but not for the rest. for P(G2 n R3) , as there're is 6 possible outcome for event G2 , but we need only 1 so 1/6 , for event R3 , there're is 6 possible outcome for it. so 1/6 x 1/6 = 1/36.... can you show me how to get $\displaystyle P(J|R3)$and $\displaystyle P(R3|J)$ please? thanks..

5. ## Re: probability of conditional events

thanks. i am able to solve the previous part using the same reasoning as in your post.