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Q.The sum of the exterior angles of a regular polygon is one-ninth the sum of the interior angles. Find the number of sides of the polygon.
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Sum of exterior angles of a polygon = 360
sum of interior angle of a polygon = (n - 2) × 180.
therefore, according to the given condition,
360 = [(n-2)×180] ÷ 9
360 × 9 = (n-2)×180
(360 × 9) ÷ 180 = n - 2
2 × 9 = n - 2
18 = n - 2
n = 18 + 2 = 20✅✅✅✅✅
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Answered by
1
Let interior angle be x and exterior angle be y
so, x + y = 180°.............(1)
the exterior angle is one-ninth of its interior angle
so, y = x/9.............(2)
substitute (2) in (1)x + x/9 = 180°
(9x + x)/9 = 180°
10x = 180° × 9
x = 18° × 9
x = 162°
so, interior angle is x = 162°
exterior angle is y = 180° - 162° = 18°
so, no. of sides of polygon = 360°/18° = 20
no. of sides of a polygon is 20
Hope it helps u!!!!
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