What is the value of p+q?

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What is the value of p+q?

by buoyant » Fri Jan 31, 2014 8:31 pm
What is the value of p+q?

(1) |p|= −|q|

(2) p=q

[spoiler]OA:A[/spoiler]
Last edited by buoyant on Mon Feb 03, 2014 7:18 am, edited 1 time in total.

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by sanju09 » Fri Jan 31, 2014 10:36 pm
buoyant wrote:What is the value of p+q?

(1) |p|= −|q|

(2) p=q

OA soon.
(1) |p|= -|q| is possible only if p = q = 0. Sufficient

(2) p = q cannot fix the value p + q. [spoiler]Insufficient

Pick A
[/spoiler]
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by buoyant » Sat Feb 01, 2014 8:13 am
OA is A indeed.

I get that from commonsense we can consider p=q=0
but, if this did not strike one's mind instantly, then one can use the absolute value eqn.

If i use this here, i get 2 values either p=-q or p=q
If above is the case, then i get either p+q= 0 or, p+q=2p or 2q

This is confusing. Can you please tell me what i am missing here?

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by [email protected] » Sat Feb 01, 2014 2:59 pm
Hi buoyant,

Your "math" explanation is too complicated for the given scenario (even you're not sure what it means, which is problematic) and takes more time to use than other approaches. The Quant section of the GMAT is NOT a math test, it's a critical thinking test that uses math as the "gauge." You should remember that fact when approaching Quant questions; there's usually several approaches to answering the given question (the "math way" often takes the longest).

DS questions are often built around Number Properties (patterns behind the math and how numbers relate to one another). In Fact 1, since you know the definition of absolute value, your instinct should be to do the easiest thing that you can: say that a minus sign in front of an absolute value means the resulting value is either negative or 0. The left side of that equation creates either a 0 or positive result. Since the two terms are equal, the only possibility is 0.

Work to build up that skill (especially on DS questions) and you'd be amazed how your score can quickly improve and any pacing problem that you may have could disappear.

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Rich
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by buoyant » Mon Feb 03, 2014 7:45 am
Hi Rich,

I understand your point and will implement the same. I would still like to learn any other way(math way)of approaching this question if you can show me one. This helps me learn concepts.

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by Bill@VeritasPrep » Mon Feb 03, 2014 11:20 am
buoyant wrote: If i use this here, i get 2 values either p=-q or p=q
If above is the case, then i get either p+q= 0 or, p+q=2p or 2q

This is confusing. Can you please tell me what i am missing here?
p can only be equal to both q and -q if q and -q are the same value.
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