SOLUTION: I've been stuck on this question on my study guide and i really need to understand how to do it An urn contains 4 white balls and 3 green balls. A set of 3 balls are drawn from

Question 946484: I've been stuck on this question on my study guide and i really need to understand how to do it
An urn contains 4 white balls and 3 green balls. A set of 3 balls are drawn from the urn. Find the probability that the third ball is white given that the first two are white.
Answer by Theo(13342) (Show Source): You can put this solution on YOUR website!

there are 4 white balls out of 7 in the urn to start with.

the probability of drawing a white ball on the first draw is therefore 4/7.

your first draw is a white ball.

there are 3 white balls out of 6 left in the urn after the first draw.

the probability of drawing a white ball on the second draw is therefore 3/6.

your second draw is a white ball.

there are 2 white balls out of 5 left in the urn after the second draw.

the probability of drawing a white ball on the third draw is therefore 2/5.

given that you drew a white ball on the first 2 draws, the probability of drawing a white ball on the third draw is 2/5 because there are 2 white balls left out of a total of 5 balls left in the urn.

that's my understanding.

RELATED QUESTIONS
My question comes from the pre-calculus CLEP study guide from collegeboard.com. It is an (answered by Fombitz)

My Alegbra Mid term study guide has stumped me on this one question which is probably... (answered by josmiceli)

Okay. This is a question on my study guide for my test tommorrow and right now I am... (answered by bmauger)

So, on my study guide there's this question I don't understand at all, what's the answer... (answered by oscargut,Alan3354)

hello, I have been stuck on a math problem and i need to know how would I do this... (answered by Alan3354)

I could use a little help with this math question for my ACT prep worksheets I've been... (answered by lwsshak3)

i have a homework question i have been doing this test and i dont understand how to do... (answered by richwmiller,drk,solver91311)

I need help with the steps to solve this problem 3b cubed minus 5b squared plus 2b... (answered by Theo)

Hi I need help on MGF1106 I have a quiz 2 study guide... (answered by solver91311)