SOLUTION: A bag contains 2 red, 1 black and 1 white ball. Peter selects one ball from the bag. He then selects a second ball but does not replace the first ball before the second ball is cho

Question 1119229: A bag contains 2 red, 1 black and 1 white ball. Peter selects one ball from the bag. He then selects a second ball but does not replace the first ball before the second ball is chosen.
a) draw a diagram showing all possibilities
b) find the probability that i) both balls selected are red ii) at least one selected ball is red
c) What is the probability that Peter had two red balls if it is known that at least one ball was red?
Answer by Boreal(15235) (Show Source): You can put this solution on YOUR website!
Red2 Black 1 White 1
R-R probability is 1/2*1/3=1/6
R-B probability is 1/2*1/3=1/6
R-W probability is also 1/6
B-R probability is 1/4*2/3=1/6
B-W probability is 1/4*1/3=1/12
W-R probability is 1/6
W-B probability is 1/12
b. Both are red has probability 1/3
At least one is red has probability is 5/6
c. If one ball is red (probability 1/2), both are red has probability 1/3, since if 1 is red, there are three other balls with three different colors, one of which is red, and that probability is 1/3

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