The interior angle of a regular polygon is twice the exterior angle. How many sides...
MATHEMATICS
WAEC 1999
The interior angle of a regular polygon is twice the exterior angle. How many sides has the polygon?
- A. 5
- B. 6
- C. 8
- D. 9
Correct Answer: B. 6
Explanation
Let the exterior angle = d
Note: Exterior angle + Interior angle = 180°
\(\implies\) d + 2d = 180°
3d = 180° \(\implies\) d = 60°
Recall, exterior angle = \(\frac{360}{\text{no of sides}}\)
\(\therefore \text{No of sides} = \frac{360}{60}\)
= 6 sides
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