A bag has seven black balls and three white balls. Two balls are drawn in sequence without replacement. Find the probability that:
a) the second ball is white.
b) the second ball is white given that the first one is black.
c) the second ball is white given that the first one is white.
Best Answer
Hint on a)
There are $7$ black balls and $3$ white balls that can be chosen to be the second ball. This with equal probability.
Hint on b)
If the first ball drawn is black then the second is drawn from a bag that contains $6$ black balls and $3$ white balls.
Hint on c)
If the first ball drawn is white then the second is drawn from a bag that contains $7$ black balls and $2$ white balls.