Question 727138: A bag contains 5 red marbles, 10 blue marbles, and 20 green marbles.
If two marbles are taken out at random, one by one, without replacement, what is the probability that they are both blue?
I know the total is 35 marbles but I am unsure how to calculate. I attempted to do 10/35, 9/34 and so forth and added all the results together but I fear it is not correct.
Answer by stanbon(75887)   (Show Source):
You can put this solution on YOUR website! A bag contains 5 red marbles, 10 blue marbles, and 20 green marbles.
If two marbles are taken out at random, one by one, without replacement, what is the probability that they are both blue?
I know the total is 35 marbles but I am unsure how to calculate. I attempted to do 10/35, 9/34 and so forth and added all the results together but I fear it is not correct.
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# of ways to pick 2 blue: 10C2 = 45
# of ways to pick a random pair: 35C2 = 595
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P(2 blue without replacement) = 45/595 = 9/119
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Cheers,
Stan H.
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