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Crazy Probability - Source: unknown

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by wizardofwashington » Thu Sep 13, 2007 3:46 pm
In a jar there are 15 white balls, 25 red balls, 10 blue balls and 20 green balls. How many balls must be taken out in order to make sure we took out 8 of the same color?

a)8
b)23
c)29
d)32
e)53

The OA says C.
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by mayonnai5e » Thu Sep 13, 2007 3:55 pm
This isn't a probability question. It asks how many balls. We need 8 of the same color so 8 white, 8 red, 8 blue or 8 green. To guarantee you get 8 of 1 color, look for the worse case: you get 7 of each color then get the 8th ball of 1 color.

7 blue + 7 red + 7 white + 7 green = 28

the next ball forces you to get at least 8 of one color so 29 must be taken out.
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by camitava » Thu Sep 13, 2007 8:47 pm
Really an interesting qs and interesting approach to solve this problem.
Correct me If I am wrong


Regards,

Amitava
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by mayonnai5e » Thu Sep 13, 2007 10:14 pm
This question actually seems more like a logical game from the LSAT than a CR from the GMAT.
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by gabriel » Thu Sep 13, 2007 11:31 pm
Hey guys,

Amitava had given a good suggestion the other day, which was, when posting a question dont give away the answer right then, i feel it somehow limits ones ability to thing freely, the OA can be given after a few days, that is after the question has been discussed. Think about it.

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by gmatguy16 » Fri Sep 14, 2007 5:33 am
I would like to add one point to what gabriel said ...if not few days back atleast give the answer 10-12 lines after the question,soemtimes what happens is immediately after looking at the question you glance at the answer and after that everything is useless!!
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by wizardofwashington » Fri Sep 14, 2007 1:52 pm
Agreed .. Point well taken.. Will make sure the next time the answers are not easily visible..Will take GMATGUY's suggestion of providing the answers at least 10-12 line after the question..
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