機會率問題再續

2.box A contains 3 red balls and 1 white ball. box B contains 2 red balls and 1 black ball. A ball is taken out at random from A and put into B. then a ball is drawn at random from B and put into box C. find the probability that
a) A contains 3 red balls.
b)B contains 3 red balls.
c)C contains the white ball.
(a)
The probability that A contains 3 red balls
=P(not get the red ball from A)
=1/4
(b)
The probability that B contains 3 red balls
=P(get the red ball from A)*P(not get the red ball from B)
=3/4*1/4
=3/16
(c)
The probability that C contains the white ball
=P(get the white ball from A)*P(get the white ball from B)
=1/4*1/4
=1/16