4 boxes, 8 ballsDiscrete Mathematics Level 4
There are four boxes. Each contains 2 balls. The first box has a red and a white ball in it. The remaining three boxes each have two white balls in them.
A ball is picked at random from box 1 and put in box 2.
Then a ball is picked at random from box 2 and put into box 3.
Then a ball is picked at random from box 3 and put into box 4.
Finally, a ball is picked from box 4.
The probability that the ball picked from box 2 is red, given that the final ball picked from box 4 is white can be written as \( \dfrac ab\), where \(a\) and \(b\) are coprime positive integers, find \(a+b\).
More probability questions
Image credit: http://wallpapertvs.com/