Question

A bag contains 6 white and 4 black balls. Two balls are drawn at random one after another
without replacement. Find the probability that both drawn balls are white.
[Ans. 1/3]

Answer 1

P (both white when 1 white) = P(both white)/P(one white)

P(both white) =

6

C

2

/

10

C

2

=1/3

P(one white) =

6

C

2

/

10

C

2

+

6

C

1

∗

4

C

1

/

10

C

2

=26/30

P (both white when 1 white) =5/13