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In the rectangular coordinate plane points X and Z lie on [#permalink]
18 Feb 2012, 15:28

00:00

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E

Difficulty:

15% (low)

Question Stats:

88% (02:10) correct
13% (00:38) wrong based on 40 sessions

Attachment:

Distance.PNG [ 4.74 KiB | Viewed 2448 times ]

In the rectangular coordinate plane points X and Z lie on the same line through the origin and points W and Y lie on the same line through the origin. If a^2+b^2=c^2+d^2 and e^2+f^2=g^2+h^2, what is the value of length XZ – length WY?

Re: In the rectangular coordinate plane points X and Z lie on [#permalink]
18 Feb 2012, 16:17

2

This post received KUDOS

Expert's post

Attachment:

Distance.PNG [ 4.74 KiB | Viewed 2427 times ]

In the rectangular coordinate plane points X and Z lie on the same line through the origin and points W and Y lie on the same line through the origin. If a^2+b^2=c^2+d^2 and e^2+f^2=g^2+h^2, what is the value of length XZ – length WY?

A. -2 B. -1 C. 0 D. 1 E. 2

Since X and Z lie on the same line through the origin then the distance between X and Z will be equal to the sum of the individual distances of X and Z from the origin: \sqrt{c^2 + d^2}+\sqrt{g^2 + h^2};

The same way, the distance between W and Y will be equal to the sum of the individual distances of W and Y from the origin: \sqrt{a^2 + b^2}+\sqrt{e^2 + f^2};

Re: In the rectangular coordinate plane points X and Z lie on [#permalink]
23 Feb 2012, 23:24

A quick question: All we know is that the line passes through X, origin, and Z vs. the second line passes through W, origin, and Y. There is no indication that the points are equidistant with respect to the origin. Can we assume this or is there a part of the wording from the original question missing?

The way I approached it: sqrt ((g-c)^2+(h-d)^2) = sqrt ((a-e)^2+ (b-f)^2) This simplifies to gc+hd = ae +bf.

Re: In the rectangular coordinate plane points X and Z lie on [#permalink]
24 Feb 2012, 00:15

Expert's post

mourinhogmat1 wrote:

A quick question: Nowhere in the question does it say that the two points are equidistant right? How can we say that the distance from origins are same? Please explain.

The formula to calculate the distance between two points (x_1,y_1) and (x_2,y_2) is d=\sqrt{(x_1-x_2)^2+(y_1-y_2)^2}. Now, if one point is origin, coordinate (0, 0), then the formula can be simplified to: D=\sqrt{x^2+y^2}.

Hence for our original question: a^2+b^2=c^2+d^2 means that points X and W are equidistant from the origin and e^2+f^2=g^2+h^2 means that points Y and Z are equidistant from the origin.

Next, since X and Z lie on the same line through the origin and W and Y lie on the same line through the origin then the distance of line segments XZ and WY is equal (for algebraic proof see above post).

Re: In the rectangular coordinate plane points X and Z lie on [#permalink]
30 May 2013, 19:29

enigma123 wrote:

Attachment:

Distance.PNG

In the rectangular coordinate plane points X and Z lie on the same line through the origin and points W and Y lie on the same line through the origin. If a^2+b^2=c^2+d^2 and e^2+f^2=g^2+h^2, what is the value of length XZ – length WY?

The above will give the answer of zero if we substitute the values from question stem.

Another way to solve this is if I draw a line segment from origin to point W (say w) and origin to point X (say x) will be hypotenuse defined by \sqrt{a^2 +b^2}= \sqrt{w^2} and \sqrt{c^2 +d^2}= \sqrt{x^2}

So you will end up with w=x and y=z --> (x+z) -(y+z) =0

gmatclubot

Re: In the rectangular coordinate plane points X and Z lie on
[#permalink]
30 May 2013, 19:29

I couldn’t help myself but stay impressed. young leader who can now basically speak Chinese and handle things alone (I’m Korean Canadian by the way, so...