SOLUTION: a bag contains red and blue marbles. you pick two marbles at random without replacing the first one. The probability of drawing a blue and then a red is 4/15. The probability th

Question 509127: a bag contains red and blue marbles. you pick two marbles at random without replacing the first one. The probability of drawing a blue and then a red is 4/15. The probability that your second marble is red if your first marble is blue is 2/3. Find the probability that the first marble is blue.
Answer by stanbon(75887) (Show Source): You can put this solution on YOUR website!
A bag contains red and blue marbles. You pick two marbles at random without replacing the first one. The probability of drawing a blue and then a red is 4/15. The probability that your second marble is red if your first marble is blue is 2/3. Find the probability that the first marble is blue.
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P(red | blue) = P(blue and red)/P(blue) = 2/3
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P(blue and red) = 4/15
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So, P(blue) = (4/15)/(2/3) = (4/15)*(3/2) = 2/5
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Cheers,
Stan H.
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