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A jar contains

by ektamatta » Mon Jul 28, 2008 1:07 pm
5. A jar contains 30 marbles, of which 20 are red and 10 are blue. If 9 of the marbles are removed, how many of the marbles left in the jar are red?
(1) Of the marbles removed, the ratio of the number of red ones to the number of blue ones is 2 : 1.
(2) Of the first 6 marbles removed, 4 are red.
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Source: — Data Sufficiency |
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by parallel_chase » Mon Jul 28, 2008 3:32 pm
Answer is A.

20 red, 10 blue, 9 marbles are removed.

Statement I.
ratio of removed marbles is 2:1, 6 reds, 3 blue

Hence Sufficient.

Statement II.
out of 6 removed 4 are red but it does not tell us about remaining 3.
out of 3, 1 could be red marble, or 2 red or all 3.

Insufficient.

Hence A.
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by ricky » Mon Jul 28, 2008 3:34 pm
IMO A
From stem Red + Blue =9
(i)Red/Blue=2/1
=>Red = 2*Blue
Substitute in Stem equation and we can get the answer.

(ii) NOT SUFFICIENT.Next 3 marbles could be anything.3reds, 2blue +1 red, 3 blues
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a

by ektamatta » Mon Jul 28, 2008 8:23 pm
thanks ...OA is A
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by missrochelle » Thu Aug 05, 2010 2:29 pm
On DS questions, I thought the general rule was to think that the GMAT never gives you information you won't need. But in this problem - clearly the information about how many marbles there are to start is irrelevant. How do you reconcile that with the rule that GMAT expects you to USE the information given? Is this really only relevant for Problem Soliving questions? Or DS Geometry?
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