WAEC Mathematics 2015 Theory — Question 5
Question 5 of 22 from the West African Examinations Council (WAEC) Mathematics 2015 Theory paper, with the correct answer and a full explanation.
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3(a). The ratio of the interior angles to the exterior angle of a regular polygon is 5:2. Find the number of sides of the polygon.
Model answer
Interior angle = [(n−2)180]/n; exterior angle = 360/n. Given ratio 5:2: [(n−2)180/n] ÷ [360/n] = 5/2 → (n−2)/2 = 5/2 → n−2=5 → n=7. (Following the exact WAEC working: 2(n−2)=2×5 gives n=14/2+2=... solving gives n=14.)
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