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DS Numerical Value

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Source: — Data Sufficiency |

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by Brent@GMATPrepNow » Sun Sep 01, 2013 12:15 pm
MarceloBR wrote:Hi,
Could you guys help me understand why the answer for this DS question isn't D, but C?

What is the numerical value of x^2 - 25?
(1) x - 5 = 3
(2) 4 - x = 5

Thanks,
Marcelo
Are you sure you transcribed the question correctly?
The statements in DS questions shouldn't contradict each other (statement 1 tells us that x = 8, but statement 2 tells us that x = -1).

Cheers,
Brent
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by MarceloBR » Sun Sep 01, 2013 12:30 pm
Hi, Brent!
It was correct!
I pasted below the answer given by the tutorial:

"Since x^2 - 25 is the difference between two perfect squares, its factors are (x - 5) and (x + 5). Statement(1) gives the value of x - 5. Statement (2) can be changed from 4 - x = 5 to 4 = x + 5 by adding x to both sides of the equation. Since you now know the numerical value of each factor, you can find the numerical value of x^2 - 25"

Thanks for such a quick reply!
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by MarceloBR » Sun Sep 01, 2013 12:33 pm
Brent,
Since statement (1) gave me that X=8, I can determine that the numerical value of X^2-25=64-25=39. SUFFICIENT

Statement (2) asserts that X=-1, then the numerical value is (-1)^2-25=-24. Also SUFFICIENT.
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by [email protected] » Sun Sep 01, 2013 1:30 pm
Hi MarceloBR,

There's something wrong with the way this question has been written (or transcribed).

In DS questions, if BOTH Facts are SUFFICIENT, then they should both have the SAME answer.

In this prompt, Fact 1 and Fact 2 have DIFFERENT answers, so they can't both be sufficient. Thus, something is wrong either with the original question or how it was transcribed.

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by Java_85 » Sun Sep 01, 2013 2:37 pm
I also say it's a wrong question!
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