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Is d negative?

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Is d negative?

by gmattesttaker2 » Mon Feb 03, 2014 10:35 pm
Hello,


I was wondering if you can please assist with the following:


Is d negative?

(1) e + d = -12

(2) e - d < -12


OA: C


Statement 1 - Insuff.
Statement 2 - Insuff.

I tried adding these 2 statements:

e + d = -12
e - d < -12

but I don't think this was giving the correct answer. I was wondering when would it be correct to add 2 statements? Thanks a lot for your help.

Best Regards,
Sri
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Source: — Data Sufficiency |

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by [email protected] » Tue Feb 04, 2014 12:52 am
Hi Sri,

This DS question asks "is D negative?" This is a YES/NO question. We know nothing about D.

Fact 1: E + D = -12

It's pretty easy to see that we don't know anything about D. The E could be positive, negative or 0, so the value of D will vary. It might be negative (YES answer), or positive (NO answer) or zero (NO answer.

Fact 1 is INSUFFICIENT

Fact 2: E - D < -12

We run into the same situation here as in Fact 1: the D could be positive, negative or 0.
Fact 2 is INSUFFICIENT.

Combined, we can actually use algebra to quickly prove what's going on.

From Fact 1, we know that E = -12 - D

Substituting that value into the inequality, we get....

(-12 - D) - D < -12
-12 - 2D < -12
-2D < 0
-D < 0
D > 0

Since D is always positive, the answer to the question is ALWAYS NO.
Combined, SUFFICIENT.

Final Answer: C

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by sanju09 » Tue Feb 04, 2014 12:53 am
gmattesttaker2 wrote:Hello,


I was wondering if you can please assist with the following:


Is d negative?

(1) e + d = -12

(2) e - d < -12


OA: C


Statement 1 - Insuff.
Statement 2 - Insuff.

I tried adding these 2 statements:

e + d = -12
e - d < -12

but I don't think this was giving the correct answer. I was wondering when would it be correct to add 2 statements? Thanks a lot for your help.

Best Regards,
Sri
You cannot get any concrete reult by adding an equation to an inequality. If sum of two quantities is negative, at least one of the two quantities must be negative. And if e - d < -12, e is smaller than d. If we take the two statements together, e is definitely negative. Let's plug in for e and d, how if e = -13 and d = 1, d is NOT negative. How if e = -7 and d = -5, it doesn't satisfy statement (2). Hence d cannot be negative at all.

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