BITSAT 2017 Paper

Let Ai(i=2,3,4,5) be the event that urn contains 2, 3, 4, 5 white balls and let B be the event that two white balls have been drawn then we have to find P(A5/B).Since the four events are equally likely we have P(B/A2) is probability of event that the urn contains 2 white balls and both have been drawn.
∴P(

B

A2

)=‌‌

2C2

5C2

=‌‌

1

10

Similarly P(

B

A3

)=‌‌

3C2

5C2

=‌‌

3

10

By Baye’s theorem,