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AS #22

by oquiella » Sat Oct 24, 2015 12:44 pm
22. What is the value of a given that a and b are real numbers.


(1) 3a + 2b = 9
(2) a = (27 - 6b)/9

PLEASE EXPLAIN WHY THEY ARE INSUFFICIENT
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Source: — Data Sufficiency |
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by MartyMurray » Sat Oct 24, 2015 6:01 pm
Statement 1 is clearly insufficient as there are an infinite number of values that would work.

Statement 2 is clearly insufficient as there are an infinite number of values that would work.

If we multiply both sides of Statement 2 by 9 we get 9a = 27 - 6b.

Rearranging a little we get 9a + 6b = 27.

Divide by 3 and get 3a + 2b = 9.

So Statement 2 is actually the same as Statement 1.

So the correct answer is E.
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by Matt@VeritasPrep » Sun Oct 25, 2015 11:49 pm
Any time you have two linear equations on the GMAT, check to see if one is simply a multiple of the other. If so, you don't have two linear equations: you have ONE, which could be trouble, especially in DS.
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