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AlexTsipkis
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IrinaOK
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Djames
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AlexTsipkis
Q. In a basket, there are 20 red balls, 30 green balls, and 50 white balls. Ten balls are taken from the basket at random. what is the probability that there are 2 red and 4 green balls.


4W, 4G, 2R

10C2 * 8C4 * 50*49*48*47*30*29*28*27*20*19
-----------------------------------------
100*99*98*97*96*95*94*93*92*91


5*7*3*5*29*7*3*3*5
-----------------------
11*97*31*23*91

4795875/69230161 = 0.069

?


Better way:

20c2 * 30c4 * 50c4 / 100c10 = 0.069
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jimjohn
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first, the total number of possible outcomes is T = (100 choose 10)

and the num of outcomes with 2 red and 4 green is
N = (20 choose 2) * (30 choose 4) * (50 choose 4)

so the final answer should be N / T

can anyone confirm if thats right?
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IrinaOK
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JingChan
jimjohn
first, the total number of possible outcomes is T = (100 choose 10)

and the num of outcomes with 2 red and 4 green is
N = (20 choose 2) * (30 choose 4) * (50 choose 4)

so the final answer should be N / T

can anyone confirm if thats right?

Yes it's right.


would agree if the question was:

what is the probability that there are exactly 2 red and 4 green balls.
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sonibubu
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Does the GMAT seriously expect you to be able to work out numbers this large, and a probability so small, in your head?
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Fistail
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AlexTsipkis
Q. In a basket, there are 20 red balls, 30 green balls, and 50 white balls. Ten balls are taken from the basket at random. what is the probability that there are 2 red and 4 green balls.


= (20c2 x 30c4 x 50c4) / (100c10)
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IrinaOK
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sonibubu
Does the GMAT seriously expect you to be able to work out numbers this large, and a probability so small, in your head?


This prob does not have AC`s that makes it diff.

one of the AC could be the not simplified version of the answer, thus would be no need to simplify.



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