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Geometry Strategy guide fourth edition P. 19 #10

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sanyu4
 Post subject: Geometry Strategy guide fourth edition P. 19 #10
 Post Posted: Tue Aug 16, 2011 7:45 pm 
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Course Students


Posts: 12
I do not understand why they used the ending equasion: 21=10.5x? 10.5x represents the area for both the triangle and the ABCE, and 21 = only represents ABCE so how can 21=10.5x?

Thank you
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jnelson0612
 Post subject: Re: Geometry Strategy guide fourth edition P. 19 #10
 Post Posted: Sat Sep 17, 2011 9:54 pm 
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ManhattanGMAT Staff


Posts: 1857
sanyu4 wrote:
I do not understand why they used the ending equasion: 21=10.5x? 10.5x represents the area for both the triangle and the ABCE, and 21 = only represents ABCE so how can 21=10.5x?

Thank you


Look again! 10.5x represents the area of ABCE; we break ABCE into a small triangle with height 3 and base x, and a rectangle with height 3 and base 3x. Thus, the triangle would have area of (3*x)/2 or 1.5x, and the rectangle would have an area of 3*3x or 9x. 1.5x + 9x = 10.5x, and we know the area of ABCE is actually 21, thus x=2.

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Jamie Nelson
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