SOLUTION: A regular polygon's interior angle is 8 times as large as its exterior angle

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Question 1011166: A regular polygon's interior angle is 8 times as large as its exterior angle
Found 3 solutions by jim_thompson5910, ikleyn, MathTherapy:
Answer by jim_thompson5910(35256) About Me  (Show Source):
You can put this solution on YOUR website!
E = exterior angle
I = interior angle

I = 8*E since the "interior angle is 8 times as large as its exterior angle"

Each pair of interior and exterior angles add up to 180 degrees
E + I = 180 degrees
E + 8*E = 180 ... replace I with 8E; solve for E
9E = 180
E = 180/9
E = 20

Each exterior angle is 20 degrees

Now let n = number of sides. We can tie n and E together with this formula

E = 360/n

Solve for n to get n = 360/E. Now plug in E = 20

n = 360/E
n = 360/20
n = 18

So there are 18 sides of this polygon.

Answer by ikleyn(52778) About Me  (Show Source):
You can put this solution on YOUR website!
.
A regular polygon's interior angle is 8 times as large as its exterior angle
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Hello,
your posting is not complete! A question is absent.
Therefore, I will add the question instead of you, as I understand it.
The question is: Find the number of sides of the polygon.
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First let us find the interior angle alpha. 
According to the condition, 

alpha%2F8  + alpha = 180°.

Hence, alpha + 8%2Aalpha = 180°*8,  or  9%2Aalpha = 180°*8,  or  alpha = %28180%5Eo%2A8%29%2F9 = 20°*8 = 160°.

Now find n, the number of sides, from the equation

%28%28n-2%29%2A180%29%2Fn = 160,  or


(n-2)*180 = n*160  -----> (n-2)*9 = n*8,  -----> 9n - 18 = 8n  -----> 9n - 8n = 18  -----> n = 18.

Answer. The number of sides of the regular polygon is 18.


Answer by MathTherapy(10552) About Me  (Show Source):
You can put this solution on YOUR website!
A regular polygon's interior angle is 8 times as large as its exterior angle
If number of sides are required, then read on!

Let number of sides be n
A regular polygon has equal angles and sides
Therefore, one of its exterior angles is: 360%2Fn (sum of exterior angles of a polygon is 360%5Eo), and one of its interior angles is: 180+-+360%2Fn
We then get: 180+-+360%2Fn+=+8%28360%2Fn%29
180+-+360%2Fn+=+2880%2Fn
180n – 360 = 2,880 ------ Multiplying by LCD, n
180n = 2,880 + 360
180n = 3,240
n, or number of sides = 3240%2F180, or highlight_green%2818%29