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# Geometry Problem

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Director
Joined: 11 Jun 2007
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Geometry Problem [#permalink]  11 Sep 2007, 17:56
I understand the answer but wondering why the 180*(n-2) formula doesn't work in this problem. There are six sides so the formula would generate 180* (6-2) = 720 but of course we know the figure is just two triangles so the answer is 360 (180*2). Please advise, thanks in advance!
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Director
Joined: 03 May 2007
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Schools: University of Chicago, Wharton School
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Re: Geometry Problem [#permalink]  11 Sep 2007, 18:02
beckee529 wrote:
I understand the answer but wondering why the 180*(n-2) formula doesn't work in this problem. There are six sides so the formula would generate 180* (6-2) = 720 but of course we know the figure is just two triangles so the answer is 360 (180*2). Please advise, thanks in advance!

this is not a case of pentagon or hexafgone. it is simply 2 triangles.
so 360.

there is another problem in OG (11 ed) looks similar to this one but bit difficult.
VP
Joined: 10 Jun 2007
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Re: Geometry Problem [#permalink]  11 Sep 2007, 18:09
beckee529 wrote:
I understand the answer but wondering why the 180*(n-2) formula doesn't work in this problem. There are six sides so the formula would generate 180* (6-2) = 720 but of course we know the figure is just two triangles so the answer is 360 (180*2). Please advise, thanks in advance!

Because it is not a polygon.
Director
Joined: 08 Jun 2007
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Re: Geometry Problem [#permalink]  11 Sep 2007, 18:13
beckee529 wrote:
I understand the answer but wondering why the 180*(n-2) formula doesn't work in this problem. There are six sides so the formula would generate 180* (6-2) = 720 but of course we know the figure is just two triangles so the answer is 360 (180*2). Please advise, thanks in advance!

Exactly
2 triangles.
Director
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oh wait! i understand now! the exterior angles are 360 (60 degrees each) but the interior angles of the polygon should be the complementary (120 degrees each) so 720 for the highlighted angles. Am I correct?
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Geometry problem 2.GIF [ 5.5 KiB | Viewed 451 times ]

CEO
Joined: 29 Mar 2007
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Re: Geometry Problem [#permalink]  11 Sep 2007, 18:15
beckee529 wrote:
I understand the answer but wondering why the 180*(n-2) formula doesn't work in this problem. There are six sides so the formula would generate 180* (6-2) = 720 but of course we know the figure is just two triangles so the answer is 360 (180*2). Please advise, thanks in advance!

Ah I remember this one from MGMAT CAT 4. Nice lil problem

The figure is basically just 2 triangles. Triangles add up to 360degrees.

720degrees would be four triangles.

ans is D.
CEO
Joined: 29 Mar 2007
Posts: 2591
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beckee529 wrote:
oh wait! i understand now! the exterior angles are 360 (60 degrees each) but the interior angles of the polygon should be the complementary (120 degrees each) so 720 for the highlighted angles. Am I correct?

Yes. There is a simple formula u can remember.

180(n-2) N is the number of sides a polygon has.

Example Triangle 180(3-2)=180

Pentagon 180(5-2)=540
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