# Thread: hi a problem of probability.

1. ## hi a problem of probability.

There are 3 bag. there are 5 white and 5 black balls in 1st bag. In the 2nd 4 white and 8 black. in the 3rd8 white n 6 black. A ball is selected randomly from first bag and put into 2nd bag. then a ball is taken from 2nd bag and put into third bag. and then a ball is taken from the third bag. Give the probability of the ball taken from third bag being WHITE.

Thank you.

2. bundho,

This problem is perfect for a tree diagram.

The first step is to select a ball from bag 1. P(white)=0.5, P(black)=0.5

The next step is to make the next set of branches -> for each possible event from bag 1, you can select a white ball or a black ball from bag 2.

The third step is to then make the branches for the possible outcomes from bag 3, based on the 4 possible outcomes from bag 1 + bag 2.

The probability of a white ball taken from bag3 is the sum of all the events where a white ball is taken from bag3, in other words, multiply the probabilities for each step of every "branch" that ends with a white ball being selected in the third step.

The answer is P(white ball from bag 3) = 0.5562

JohnM

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