## anonymous 5 years ago three jars contain colored balls as follows: Jar Red White Blue I 10 1 9 II 2 5 13 III 9 1 10 One jar is chosen at random and a ball is withdrawn. The ball is red. What is the probability that it came from jar I? Round to four decimals

1. anonymous

So there's a $$\frac{1}{3}$$ chance that the jar you chose was jar one, and a $$\frac{10}{20}$$ chance that you chose a red ball if you the first jar. Now you need to combine these two numbers to get the overall probability you're looking for. Do you know how to combine them?

2. anonymous

you do you mean like multiple 1/3 by 10/20

3. anonymous

Exactly. Does that make sense?

4. anonymous

i got an answer of .1667 but when i put it as my answer it says its wrong

5. anonymous

Hm. Odd. Let me think on it.

6. anonymous

There's a chance that what it's looking for is--given the fact that you already chose a red ball, what are the chances it was in the first jar. In that case, you realize that there are $$21$$ ways to get a red ball. $$10$$ of those ways are in the first jar, so you can get the probability from there.

7. anonymous

so i would multiple 10 times 21

8. anonymous

So the probability would be... out of the $$21$$ overall chances, how many occur in the first jar. That would be dividing the two.

9. anonymous

okay now I got it thanks alot