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docabuzar
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GMAT 1: 610 Q43 V31
GMAT 1: 610 Q43 V31
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Combinations 24 Jan 2012, 14:18
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Two questions?

Q.1 What topics within combinotronics to cover for GMAT? Since there are so many variations in combinations, permutations, circular & linear arrangements.

Q.2 How to deduce the final result quickly if our formula shows something like this:
= 8! - (7!*2) - (5!*2) = ??



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Bunuel
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Combinations 24 Jan 2012, 14:41
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docabuzar
Two questions?

Q.1 What topics within combinotronics to cover for GMAT? Since there are so many variations in combinations, permutations, circular & linear arrangements.

Q.2 How to deduce the final result quickly if our formula shows something like this:
= 8! - (7!*2) - (5!*2) = ??
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Hi, and welcome to GMAT Club!

Q #1: Try Combinatorics chapter of Math Book to have an idea about the staff that is tested on the GMAT: math-combinatorics-87345.html

Also try some questions on combinations to practice:
DS: search.php?search_id=tag&tag_id=31
PS: search.php?search_id=tag&tag_id=52
Hard questions on combinations and probability with detailed solutions: hardest-area-questions-probability-and-combinations-101361.html

In addition, note that usually the GMAT combination/probability questions are fairly straightforward and as practice shows you won't encounter more than 2-3 questions from this field.

Q #2: 8! - (7!*2) - (5!*2) --> factor out 5!*2 --> 5!*2*(6*7*4-6*7-1)=240*125=30,000.

Hope it helps.

P.S. Please post general math questions in the main Math forum. Thanks.



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Hi there,
This topic has been closed and archived due to inactivity or violation of community quality standards. No more replies are possible here.
Where to now? Join ongoing discussions on thousands of quality questions in our Quantitative Questions Forum
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Thank you for understanding, and happy exploring!