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Please answer; "There are 640 marbles in a bag. There are red, blue, and green marbles. After losing a total of 47 green and blue marbles, there are a total of 113 green and blue marbles left. Assuming you still had all the marbles, what are the odds of drawing a red marble two times in a row?"

LunarRoxey  Apr 4, 2017
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#1
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Originally there must have been 123 + 47 = 170 green and blue marbles,  meaning there are 640 - 170 = 470 red marbles.

The bag now has 640 - 47 = 593 marbles in total.

Assuming you are only going to draw two marbles out of the bag (rather than continuing to draw all of them out), the probability of getting two reds is (470/593)*(469/592)  ≈ 0.63

(if you meant that you continue to draw out all the marbles, then the probability of getting two reds in a row at some point is 1. i.e. it is certain, because there are so many more red marbles than blue and green.)

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Alan  Apr 4, 2017
edited by Alan  Apr 4, 2017
edited by Alan  Apr 4, 2017
#2
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Thanks for the help!

LunarRoxey  Apr 4, 2017

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