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Four balls in a bag respectively are red, blue, yellow, and [#permalink]
22 May 2005, 10:25

Four balls in a bag respectively are red, blue, yellow, and green. If two balls are selected at random, what is the probability that one of them is green or blue?

total possible couples : (4*3)/2 = 6
couples of balls with G : GY, GB, GR
couples of balls with B (other than GB) : BY, BR
total positive outcomes (couples G + couples B) / total possible couples
5/6

Re: Probab - balls [#permalink]
03 Jun 2005, 12:29

pb_india wrote:

Four balls in a bag respectively are red, blue, yellow, and green. If two balls are selected at random, what is the probability that one of them is green or blue?

when the question states that one of them is green or blue does that mean only one or at least one

i assumed it means only one and got an answer of 2/3

however others have assumed at least one, thus including the possibility of getting green and blue and getting an answer of 5/6

If it says one of two is such and such then the other one could be anything. If it is "exactly one" then the question must have the word "exactly" in there. _________________

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