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Geometry Doubt.

Problem Solving — algebra and arithmetic (GMAT Focus Edition)
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Geometry Doubt.

by sachindia » Sat Jan 26, 2013 2:16 am
Hi ,
I read the following in somebody's handout..
how true is the exception mentioned..

If two lines are perpendicular to each other, the product of their slopes is -1. (m1 m2 = -1). (There is one
exception to this rule - when two lines are parallel to x and y axis respectively, then m1 m2 ≠ -1, even if the
lines are perpendicular).
Regards,
Sach
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by ceilidh.erickson » Sat Jan 26, 2013 7:10 am
The reason that the product of the slopes of lines parallel to the x and y axis will not be -1 is this: any line parallel to the x axis will have a slope of 0 (rise 0 / run... infinity), and any line parallel to the y axis will have a slope that is undefined (rise infinity / run 0). Any time you're dividing by 0, the fraction is undefined. If we multiply the slopes, 0 * undefined = undefined.

I've never seen this rule directly tested on a GMAT question, but of course it's possible that they might test it. (The GMAT very rarely asks about situations in which a ratio is undefined). Almost always, when the GMAT is testing perpendicular lines on a coordinate plane, they'll give slopes such as 1/3 and -3; these are negative reciprocals whose product is -1.
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by sachindia » Sat Jan 26, 2013 8:06 am
amazing.. . thanks ceilidh.
I have a couple of questions.. got my gmat the coming thursday.

Do we need to remember the GMAT codes of 5 schools to which we want to send the scores or do we need to select the names from the drop down ?
Say, I want to do my mba 2 years from now.. So after 2 years when I apply, do I need to send the scores again?


Are we given limited scratch papers or can we ask for as many as we need. .
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Sach
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by ceilidh.erickson » Tue Jan 29, 2013 11:38 am
No, you won't need to memorize the codes of the schools you want. There will be a drop-down menu.

You won't need to resend the scores - once you've sent them, the schools will keep them for up to 5 years (after which time the GMAT scores expire).

You will be given one pad of laminated scrap paper. If you run out, they'll bring a new one and take away the old one. I'd recommend getting a fresh pad during each break so you don't run out.

Good luck!
Ceilidh Erickson
EdM in Mind, Brain, and Education
Harvard Graduate School of Education
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