There are 2 boxes. First contains 6 red, 5 green and 9 white balls whereas second contains 10 red, 4

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07 Sep 2012 probability

There are 2 boxes. First contains 6 red, 5 green and 9 white balls whereas second contains 10 red, 4 green and 6 white balls. If 1 ball is selected at random from one of the boxes, then probability of getting green ball will be

OPtion

1) 1/2
2) 3/8
3) 9/20
4) 9/40
5) 11/40
6) 1/4
7) 3/20
8) 2/5
9) 1/3
10) none of these

Solution

probability of selecting box = 1/2
probability of selecting green ball from first box = 5/20
probability of selecting green ball from second box = 4/20
so net probability = 1/2(5/20) + 1/2(4/20) = 9/40

Correct Option: 4 Best Solution (0)