Problem with an answered question

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Problem with an answered question

by datonman » Sat Nov 15, 2014 5:45 pm
This is in regards to a previous answered question posted here. But apparently I didn't get any of the explanations given. I went over the explanation for the following problem:

A square with area 25 has one vertex on point (-2,1)in the coordinate plane. From the table below, select the x and y coordinates that could correspond to another vertex of the same square. There's an attachment for the following answers.

Someone posted an answer that and I quote him/her "when you draw a diagonal line on a graph, you can draw a right triangle with THAT diagonal line as its hypotenuse."

What does that mean exactly? That's where I got confused. What way would the line be made?
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Problem with an answered question

by [email protected] » Sat Nov 15, 2014 6:52 pm
Hi datonman,

You're referring to this series of posts:

https://www.beatthegmat.com/a-square-wi ... 77233.html

Since I'm the one that you're quoting, I'll be happy to provide some additional info on this math concept. You'll likely find it most helpful to go through the steps, so I'll walk you through them all, but you should physically go through the steps on a piece of paper.

1) Draw a graph.
2) Graph the points (-2, 1) and (-5, -3) and connect these two points with a line segment.
3) Now graph the point (-5, 1). Connect this point to (-2,1) and to (-5, -3). You should now see a right triangle.
4) What are the lengths of the horizontal and vertical lines that you just drew? (3 and 4, respectively).

5) So you have a right triangle with sides of 3 and 4. The third side (the diagonal) has to be 5 (which matches up with what the prompt told us about the square).

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by datonman » Sat Nov 15, 2014 7:00 pm
Hello,

Thank you for getting me back to me on such short notice. I'm just a little confused. (Maybe it's because I've been studying for three hours and my brain is overworked.) But for 2.) I'm assuming that the -5, -3 was from the answer choices. Was this a quick choice using logic?

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by [email protected] » Sat Nov 15, 2014 11:02 pm
Hi datonman,

The deductions here are based on a multi-step process:

1) Since the square has a side length of 5, we can draw a line segment with a length of 5 into the graph as a diagonal line.
2) The two sides of the right triangle that you can draw based on THAT diagonal MUST have side lengths of 3 and 4.
3) "-5" is "3 away" from -2 and "-3" is "4 away" from 1.

It certainly helps having those numbers in the answer choices though.

GMAT assassins aren't born, they're made,
Rich
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