# Math forum

 finding the missing angles Options
lqudduskhan
 #1 Posted : Wednesday, March 16, 2011 3:43:24 PM
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if there is a shape given, how can we tell whether the sum of its angles is 180 degree or 360 degree?

johan
 #2 Posted : Wednesday, March 16, 2011 4:01:42 PM

Joined: 1/26/2011
Posts: 22

Hi

If we are given a convex polygon with n sides and S is the sum of the measures of the interior angles then S = 180(n - 2).

So if we have a shape with four angles the sum of the angles is;

S=180(4-2)=360 degrees

If we have a shape with three angles then the sum of the angles is;

S=180(3-2)=180 degrees

lqudduskhan
 #3 Posted : Wednesday, March 16, 2011 4:07:44 PM
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i was given a pentagon type shape, 2 of the angles were given, i had to find 'h' but the sum was 360 degree not 180 degree, why is that so?

johan
 #4 Posted : Wednesday, March 16, 2011 4:28:29 PM

Joined: 1/26/2011
Posts: 22

Sounds very weird since the internal angles of a simple pentagon sum is 540 degrees.Since:

S=180(5-2)=540 degrees
Are you sure that its convex?
lqudduskhan
 #5 Posted : Wednesday, March 16, 2011 5:19:38 PM
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im in grade 7, please can u explain me this formula to tell whether the sum of the angles is 180 degrees or 360 degrees, i can't understand it.

johan
 #6 Posted : Wednesday, March 16, 2011 6:19:56 PM

Joined: 1/26/2011
Posts: 22

Sure!

I you for example have a triangle (three angles) then in order to determine the sum of a triangle you multiply 180 with then number of angles minus 2:

If we have a square then you multiply 180 with then number of angles minus 2:

If we have a pentagon (five angles) we get:

Did this help?

mohit
 #7 Posted : Wednesday, March 16, 2011 9:58:14 PM

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@johan

i think he is saying that the sum of those two angles is given to be 360 which is obviously possible in a pantagon...

@khan..

can u please tell me the question...m not getting what is "h"..

lqudduskhan
 #8 Posted : Thursday, March 17, 2011 11:22:51 AM
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@ johan: thanku so much for your help

@ mohit: thanku so much, i have understood

funke
 #9 Posted : Saturday, September 24, 2011 6:48:49 PM
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Joined: 7/17/2012
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i had to find 'h' but the sum was 360 degree not 180 degree, why is that so?

Tiket Pesawat Murah

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