geomatry

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geomatry

by vipulgoyal » Sun Jan 26, 2014 10:18 pm
As the figure shown above, the rectangular region consists of 20 square with side of 1 unit each .What is the area of the triangle?
please refer attachment
I got it right by subtracting three trangles from one rectangle I am looking for alt and fast approach
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by GMATGuruNY » Mon Jan 27, 2014 5:25 am
vipulgoyal wrote:As the figure shown above, the rectangular region consists of 20 square with side of 1 unit each .What is the area of the triangle?
please refer attachment
I got it right by subtracting three trangles from one rectangle I am looking for alt and fast approach
If we omit the bottom row, what remains is a rectangle circumscribing the triangle.
The area of this rectangle = 3*5 = 15.
The triangle constitutes less than 1/2 of the rectangle.
Thus, the correct answer choice must be LESS than 7.5.
It is possible that only one answer choice will be viable, as in the following problem from GMATPrep:

https://www.beatthegmat.com/area-of-pqr-t115199.html
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by Brent@GMATPrepNow » Mon Jan 27, 2014 7:27 am
Image
First notice that the entire rectangle has an area of 20
Image

Now find the area of each piece that is NOT part of the red triangle.
Image

So, the area of the red triangle = (area of big rectangle) - (total area of green parts)
= 20 - (3 + 3 + 2.5 + 5)
= 20 - (13.5)
= 6.5

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Brent
Brent Hanneson - Creator of GMATPrepNow.com
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