Ed put some blue marbles and some red marbles into a bag. He then asked Phil to reach into the bag, without looking in, and draw out a marble. Phil drew out a blue marble. Ed asked Phil to draw out another marble and, once again, Phil drew out a blue marble.
"There must be more blue than red marbles in the bag," said Phil. "I wonder what the probability is of my drawing out another blue marble on my third try?"
Ed replied, "Exactly nine tenths of what it was of drawing a blue marble on your first draw."
Ed told Phil that he had put "ten, give or take two or three" marbles into the bag. How many marbles were in the bag at the start?
10 points goes to the correct answer with the clearest explanation!
Thank you.
2007-01-02
04:03:57
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7 answers
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asked by
Anonymous
in
Mathematics