BITSAT 2013 Paper

For k = 1, 2, 3 the box Bk contains k red balls and (k + 1) white balls. Let P (B1) =

1

2

, P (B2) =

1

3

and P (B3) =

1

6

. A box is selected at random and a ball is drawn from it. If a red ball is drawn, then the probability that it has come from box B2, is