GMAT Geometry

moneyman · Posted: Wed May 07, 2008 6:39 am Post subject: GMAT Geometry

Pls explain guys!!

Ans E

amitansu · Posted: Wed May 07, 2008 8:43 am Post subject:

A is answer here.

from 1) we can say line K is vertical (since slope is undefined)
and line m is horizontal since slope is 0.

So can be concluded that both are perpendicular.

From 2) we can conclude that K is vertical, since slope is undefined.
But no data regarding line m to define whether it is horizontal.So insufficient.

dk_gmat · Posted: Wed May 07, 2008 8:49 am Post subject:

Hi there ,

For problems involving Co-ordinate Geometry best way is to draw basic simple diagrams.

Since the co-ordinates are pretty simple, draw a square and bisect the sides and produce them inward so that they intersect at a point.

Now the point of intersection may be considered as the origin (0,0).

Now two points given in the Questions coincide with two vertices of the square .

If you note both the statements give exact location and direction of line k.

K is the perpendicular to the X axis or the horizontal axis .

But what would be the orientation of line m is not known.

The line m may or may not be parallel to X - axis.

Hence both the statements together is not sufficient to answer the Question.

Hence answer is E.

DK... Very Happy

amitansu · Posted: Wed May 07, 2008 9:00 am Post subject:

yes you are right !!

i didn't see that there is only one ref. point (1,-1) for line m.
the other point is not defined.

Though the approach was correct.

dk_gmat · Posted: Wed May 07, 2008 9:05 am Post subject:

Hey Amit,

No worries

We all are here to help each other and rise together !!!!

DK .... Very Happy

amitansu · Posted: Wed May 07, 2008 9:09 am Post subject:

amen...

moneyman · Posted: Wed May 07, 2008 9:29 am Post subject:

Im sorry guys but I have still not underdstood the problem..I am bad at lines and angles..So pls explain in an easier way

Also pls tell me what to look out for in this question while trying to solve it.

What is the condition required for two lines to be parallel or perpendicular and what role does the slope play in finding out whether two lines are perpendicular or not??

Monday is my exam so I am concentrating more oin the basics..your help will be really appreciated!!

amitansu · Posted: Wed May 07, 2008 9:53 am Post subject:

First thing : For two lines to be perpendicular with each other, their slopes' multiplication should be -1. (chk this if two slope are known to you)

Also : The slope of a horizontal line is always 0.(Rule)
The slope of the vertical line is undefined. (Rule)
Two lines to be parallel the two slopes should have same value
with same sign.
Here from the 1st statement we can know the slope of the line (one point being (1,1) and other one is (1,-1).Because this is a common point of intersection of two lnes.
So slope is m=1-(-1)/1-1, which is undefined.So line is vertical.

From statement 2 : we don't get any characteristic of line m's slope, since it 's given only one point of reference for line m which is (1,-1).We need two coordinate points of (x,y) to know the slope.

Btw, is your GMAT test on Monday !!

However , all the best for your test.

Amit