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DS - Probability

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DS - Probability

by oks » Fri Sep 12, 2008 4:13 pm
If a bottle is to be selected at random from a certain collection of bottles, what is the probability that the bottle will be defective?
(1) The ratio of the number of bottles in the collection that are defective to the number that are not defective is 3:500.
(2) The collection contains 3,521 bottles.

Answer: A

Why not C?

Would not we want to know the total number of bottles in order to use the probability formula = desired/possible?

Thanks!
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Source: — Data Sufficiency |
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Re: DS - Probability

by gmat2010 » Fri Sep 12, 2008 4:27 pm
oks wrote:If a bottle is to be selected at random from a certain collection of bottles, what is the probability that the bottle will be defective?
(1) The ratio of the number of bottles in the collection that are defective to the number that are not defective is 3:500.
(2) The collection contains 3,521 bottles.

Answer: A

Why not C?

Would not we want to know the total number of bottles in order to use the probability formula = desired/possible?

Thanks!
Statement 1 gives you the ratio which you can figure out the probability.
3 defective, 500 non defective, 503 total
therefore, 3/503 is the probability of defective.

2. not sufficient.

the answer is A.
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