# Thread: Help with son's probability question

1. ## Help with son's probability question

Hi Folks,

I'm new here. Haven't studied probability in 30 years and trying to help my son with his homework. In the attachments is the question, if you wouldn't mind helping. Thank you.

Brian

2. ## Re: Help with son's probability question

Try visualizing all the possibilities in a 2-by-2 table.

3. ## The Following User Says Thank You to staassis For This Useful Post:

mackbri (09-05-2014)

4. ## Re: Help with son's probability question

Thank you for your help. I figured out parts 1 and 2....stuck on part 3.

5. ## Re: Help with son's probability question

hi,
it is a straightforward application of the Bayes theorem:

P(D|R) = P(R|D)*p(D)/(p(R|D)*p(D)+p(R|W)*p(W))

Where D is dry, R is reaches the top and W is wet. The respective probabilities are all defined in the problem .

regards
rogojel

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