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Bea's CDs

by Brent@GMATPrepNow » Thu Jan 29, 2009 2:21 pm
Bea owns how many more CDs than Al owns?
(1) If Bea gives 9 of her CDs to Al, then Al will own twice as many CDs as Bea owns.

(2) If Bea gives 1 CD to Al, and Al purchases 4 additional CDs, then Al and Bea will have an equal number of CDs.

Please note that this is not an official GMAT question; it’s my attempt to create difficult (650+ level) GMAT-style questions for this forum.
Last edited by Brent@GMATPrepNow on Thu Jan 29, 2009 6:49 pm, edited 1 time in total.
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by dmateer25 » Thu Jan 29, 2009 5:57 pm
Brent,

Is statement one supposed to be: If Bea gives 9 of her CDs to Al, then Al will own twice as many CDs as Bea owns?


If so, I will go with B.

(2) If Bea gives 1 CD to Al, and Al purchases 4 additional CDs, then Al and Bea will have an equal number of CDs.

B = Bea
A = Al

B-1 = A + 1 + 4
B = A + 6

Bea owns 6 more cd's than al
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by Brent@GMATPrepNow » Thu Jan 29, 2009 6:49 pm
Is statement one supposed to be: If Bea gives 9 of her CDs to Al, then Al will own twice as many CDs as Bea owns?
Oops. Yes, you're exactly right, dmateer25. Right about the wording (which I have now changed) and right about the answer (B).

Here's my full solution as well:

Let A = number of CDs Al has and let B = number of CDs Bea has.
We want to determine the value of B – A

(1) We can create the equation 2(B-9) = A+9
Simplify this to get 2B-18= A+9
Or 2B-A=27
This does not tell us the value of B-A. INSUFF.

(2) We can create the equation B-1 = A+1+4
Simplify this to get B-A= 6
SUFF (Bea has 6 CDs more than Al has)

Answer = B
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Re: Bea's CDs

by sanjay_dce » Fri Jan 30, 2009 11:03 pm
Brent Hanneson wrote:Bea owns how many more CDs than Al owns?
(1) If Bea gives 9 of her CDs to Al, then Al will own twice as many CDs as Bea owns.

(2) If Bea gives 1 CD to Al, and Al purchases 4 additional CDs, then Al and Bea will have an equal number of CDs.

Please note that this is not an official GMAT question; it’s my attempt to create difficult (650+ level) GMAT-style questions for this forum.



an easy/quick way to solve such kind of DS question is:
the question stem ask about diff b/w B and A.

1) stmt1 gives an equation but in multiple terms of one of the variable A hence A-B can't be found out( no common factor)
2) stmt 2 gives a equation where there is no multiplier of A or B hence B-A can be found out. it will take 5-10 seconds atmost if such thinking is realised

hence Ans is B
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by vikram_k51 » Tue Feb 03, 2009 7:37 am
Bea owns how many more CDs than Al owns?
(1) If Bea gives 9 of her CDs to Al, then Al will own twice as many CDs as Bea owns.

(2) If Bea gives 1 CD to Al, and Al purchases 4 additional CDs, then Al and Bea will have an equal number of CDs.

From A: 2x-y=27;Not Sufficient

From B: x-y=6;Sufficient

Hence B
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