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Coordinate Plane Question from GMAT Prep 1

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MIT_Aspirant
 Post subject: Coordinate Plane Question from GMAT Prep 1
 Post Posted: Mon Aug 25, 2008 8:21 pm 
Does the line K intersect quadrant II?

(1) The slope of k is -1/6
(2) The y intercept of k is -6

This is a DS question, the answer is A. Can someone explain to me how we can make this determination simply by the slope of the line? Is there a rule which allows for the derivation of the same?
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Genie
 Post subject: Solution
 Post Posted: Tue Aug 26, 2008 2:43 pm 
Here is what I do, although this is a bit quirky :)

I always imagine the origin of the line to be somewhere in texas. Now Positive Slope = Going towards Pennisylvania (P common between the terms : ) ) and negative slope = going towards Nevada :)

Now consider the Map of the US; and say your quadrants were infinitesimally large, you'll see that no matter what, if you have a negative slope, at one time or the other (no matter what the intercept is) the line will always pass through the second quadrant.
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MIT_Aspirant
 Post subject:
 Post Posted: Tue Aug 26, 2008 6:25 pm 
thanks genie.

or we can relate to negative as going south :)

One a more serious note, I get this now - the logic is unless the line is vertical - if the line has positive slope - i.e. a tilt towards the right it will eventually enter quadrant 1 somewhere, conversely if the line has a negative slope- i.e. a tilt towards the left it will enter the quadrant 2 sometime.

Thanks.
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RonPurewal
 Post subject:
 Post Posted: Sun Sep 07, 2008 1:49 am 
Offline
ManhattanGMAT Staff


Posts: 7146
MIT_Aspirant wrote:
or we can relate to negative as going south :)


only as you go to from left to right. if you're going from right to left, then a negative slope actually goes "north".
i'm not trying to be annoying; i'm posting this for the sake of those posters whose native languages run from right to left, and who therefore might be confused by the automatic assumption of reading from left to right.
fortunately, north is up everywhere. (sorry aussies)

things like this are probably best individualized - make up your own favorite mnemonic device, and remember it. but if you like anyone else's idea, feel free to adopt it.
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