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probability hats

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probability hats

by jzebra10 » Tue Nov 29, 2011 12:06 am
Please explain how to answer.

A box has 6 red hats and 5 green hats. What is the probability of drawing at least one green hat in two consecutive drawings if the hat is not replaced?

a) 10/11
b) 8/11
c) 7/12
d) 5/13
e) 2/7
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by Anurag@Gurome » Tue Nov 29, 2011 12:23 am
jzebra10 wrote:Please explain how to answer.

A box has 6 red hats and 5 green hats. What is the probability of drawing at least one green hat in two consecutive drawings if the hat is not replaced?

a) 10/11
b) 8/11
c) 7/12
d) 5/13
e) 2/7

Probability of drawing at least one green hat in 2 consecutive drawings = 1 - probability that both the hats are red
Now, probability that both hats are red = 6/11 * 5/10 = 3/11 (since there is no replacement)
Therefore, required probability = 1 - 3/11 = [spoiler]8/11[/spoiler]

The correct answer is B.
Anurag Mairal, Ph.D., MBA
GMAT Expert, Admissions and Career Guidance
Gurome, Inc.
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