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LvsPnthers
03-06-2008, 05:19 AM
There are 5 RED marbles and 7 BLUE marbles in a bag. One RED marble is taken out and put back. What is the probability that the next marble taken out will be BLUE so that the sequence of marbles removed is 1 RED and 1 BLUE? Explain.

THEN suppose that the RED marble is NOT put back in the bag. What is the probability that the next marble taken out will be BLUE so that the sequence of marbles removed is 1 RED and 1 BLUE? Explain.

tkhunny
03-06-2008, 10:33 AM
From 5 red & 7 blue
1 red -- 5/(5+7) = 5/12
Put it back
From 5 red & 7 blue
1 blue -- 7/(5+7) = 7/12

From 5 red & 7 blue
1 red -- 5/(5+7) = 5/12
Don't put it back
From 4 red & 7 blue
1 blue -- 7/(4+7) = 7/11