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riddle: lots of marbles...

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Old Aug 6, 2002 | 08:47 AM
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Default riddle: lots of marbles...

PLEASE DO NOT LOOK UP THE ANSWERS ON THE INTERNET AND POST THEM HERE. If you want to look up the answers that's fine. The answers are out there, they are not that hard to find. Some people like to try and solve the riddle before giving up and looking up the answers. This is for those people. Enjoy...


you have two jars, 50 red marbles, 50 blue marbles. you need to place all the marbles into the jars such that when you blindly pick one marble out of one jar, you maximize the chances that it will be red. (when picking, you'll first randomly pick a jar, and then randomly pick a marble out of that jar) you can arrange the marbles however you like, but each marble must be in a jar.
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Old Aug 6, 2002 | 09:03 AM
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what if you just put one red marble in the one jar and the other 99 marbles in the other jar...i don't feel like crunching the numbers, but i think that would be near 75% chance of drawing a red.

i finally got a chance to answer!!! i'm sure that someone will beat me with a better answer though.
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Old Aug 6, 2002 | 09:09 AM
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Assuming a standard-shaped jar and assuming you just grab a random marble out of the top of each jar, just put 25 blue marbles in the bottom of each jar and 25 red marbles on the top of each jar.

But i'm sure there's more to it than that.... what am i missing?
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Old Aug 6, 2002 | 09:11 AM
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[QUOTE]Originally posted by Hegulator
[B]Assuming a standard-shaped jar and assuming you just grab a random marble out of the top of each jar, just put 25 blue marbles in the bottom of each jar and 25 red marbles on the top of each jar.

But i'm sure there's more to it than that....
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Old Aug 6, 2002 | 10:15 AM
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[QUOTE]Originally posted by Hegulator
[B]Assuming a standard-shaped jar and assuming you just grab a random marble out of the top of each jar, just put 25 blue marbles in the bottom of each jar and 25 red marbles on the top of each jar.

But i'm sure there's more to it than that....
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Old Aug 6, 2002 | 10:50 AM
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Originally posted by lehighwiz


i considered that, but the randomness of the draw will eliminate that as an option i think.

allright, i did the math:

((1/1)*100)/2 + ((49/99)*100)/2 = 74.74%
Same answer I arrived at. I vaguely remember being asked this before, and I do believe this is the correct answer.
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Old Aug 6, 2002 | 11:55 AM
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[QUOTE]Originally posted by Hegulator
[B]Assuming a standard-shaped jar and assuming you just grab a random marble out of the top of each jar, just put 25 blue marbles in the bottom of each jar and 25 red marbles on the top of each jar.

But i'm sure there's more to it than that....
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Old Aug 6, 2002 | 11:59 AM
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Originally posted by lehighwiz


i considered that, but the randomness of the draw will eliminate that as an option i think.

allright, i did the math:

((1/1)*100)/2 + ((49/99)*100)/2 = 74.74%
Yes, that is the highest probability you can achieve. Nice work guys. I also had a few PM's with the correct answer.

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