SOLUTION: A bag contains 3 black and 2 white balls. Two balls are taken from the bag at random, without replacement. By drawing a tree diagram, or otherwise, calculate the probability that

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Question 1196516: A bag contains 3 black and 2 white balls. Two balls are taken from the bag at random, without replacement. By drawing a tree diagram, or otherwise, calculate the probability that
(a) both balls are black,
(b) at least one ball is white
(c) the two balls are the same colour.

Answer by ikleyn(52798) About Me  (Show Source):
You can put this solution on YOUR website!
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A bag contains 3 black and 2 white balls.
Two balls are taken from the bag at random, without replacement.
By drawing a tree diagram, or otherwise, calculate the probability that
(a) both balls are black,
(b) at least one ball is white
(c) the two balls are the same colour.
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(a)  P(both balls are black) = C%5B3%5D%5E2%2FC%5B3%2B2%5D%5E2 = C%5B3%5D%5E2%2FC%5B5%5D%5E2 = 3%2F10 = 0.3 = 30%.


(b)  P(at least one ball is white) = 1 - P(both balls are black) = 1+-+3%2F10 = 7%2F10 = 0.7 = 70%.


(c)  P(the two balls are the same colour) = P(both are black) + P(both are white) =

      = 0.3 + C%5B2%5D%5E2%2FC%5B5%5D%5E2 = 0.3 + 1%2F10 = 0.4 = 40%.

Solved.