Urn a contains 9 yellow balls and 6 red balls. urn b contains 5 yellow balls and 12 red balls. urn c contains 11 yellow balls and 12 red balls. an urn is picked randomly (assume that each urn is equally likely to be chosen), and then a ball is picked from the selected urn. what is the probability that the chosen ball came from urn b, given that it was a yellow ball?

Hello!

To find the probability of a compound event, you have to multiply the probabilities of each event it contains. In this case, our two events are selecting B, and selecting a yellow ball from B.

First off, there is a 1/3 chance of selecting B. This is the probability of the first event.

Next, we know that urn B has 5 yellow balls and 12 red balls. This means there are 17 total balls, so there are 5/17 yellow balls. This will be our second probability.

Finally, we multiply our two probabilities. 1/3(5/17)=5/51

The probability is 5/51, or about 10%.

I hope this helps!