GMAT preb prob

This topic has expert replies
Source: — Data Sufficiency |

User avatar
GMAT Instructor
Posts: 509
Joined: Wed Apr 21, 2010 1:08 pm
Location: Irvine, CA
Thanked: 199 times
Followed by:85 members
GMAT Score:750

by tpr-becky » Wed May 26, 2010 8:59 am
For this problem we need to know whether X was in the top six contributing countries. We know that The top 6 contributed 67.8% of 1.6 Billion from the question stem.

Statement 1 says that X is not in the top 4 because the top 4 contributed more than X and it tells us that numbers 5 and 6 contributed a total of 11.8% (67.8-56) - but it doesn't tell us how much X contributed compared to the other countries. So this cannot be enough information.BCE

Statement 2 tells us the total percent country X spent but it doesn't tell us what that number would be in comparison to the other countries and since the top 6 contributed 67.8% we can't know whether X's 4.8% is in the top 6.

CE

If you put them together wehave more information, we know that numbers 5 and 6 contributed 11.8% and that X contributed 4.8%. But it doesn't tell us whether X is in that top 6 becuase numbers 5 and 6 could have each contributed 5.9% which would mean X is not in the top six, or 5 could have contributed 7% and x could have contribued 4.8% and been in the top 6 therefore the answer is E.
Becky
Master GMAT Instructor
The Princeton Review
Irvine, CA

User avatar
Legendary Member
Posts: 1460
Joined: Tue Dec 29, 2009 1:28 am
Thanked: 135 times
Followed by:7 members

by selango » Wed May 26, 2010 10:09 am
Great explanation becky!!!Thanks

User avatar
GMAT Instructor
Posts: 1052
Joined: Fri May 21, 2010 1:30 am
Thanked: 335 times
Followed by:98 members

by Patrick_GMATFix » Wed May 26, 2010 1:05 pm
I really don't like to get questions like this but inevitably you will get at least one. Basically one approach to evaluating statements for theses types ofquestions is to do your best to create a case in which the question is answered with a YES and a case in which the question is answered with a NO. If using the data from a statement, you can create both cases, the statement is definitely insufficient. On the other hand, if whichever case you come up always answers the original question the same way (only YES or only NO), then the statement is sufficient.

Merging the statements works the same way. In this question, when evaluating both statements we could build the following cases:

Case 1: Top 4=16% each. 5th=7%. X=4.8%. Remaining 153 countries=tiny%
Case 2: Top 4=16% each. 5th=6.8%. 6th=5%, X=4.8% Remeaining 152=tiny%

In the first case the question "Is X in the top 4" would be answered with a YES. In the 2nd casee, the question would be answered with a NO. So we don't have sufficiency. The answer is E

If this still doesn't make much sense, study the detailed solution and the video solution at GMATPrep question 1491

-Patrick