WAEC 2015 Mathematics · Question 37

The population of students in a school is 810. If this is represented on a pie chart, calculate the sectoral angle for a class of 72 students

Options

A.32o
B.45o
C.60o
D.75o

Answer: A. 32o

Explanation written with AI and checked against the answer key

Analyze the question: A pie chart represents the whole population as 360°. We need the angle for a class of 72 students out of 810. Concept: Sectoral angle = (part ÷ whole) × 360° Solution: Sectoral angle = (72 ÷ 810) × 360° Simplify 72/810: divide both by 18 → 4/45 Then: (4/45) × 360° = 4 × 8° = 32° Check: 360 ÷ 45 = 8, and 8 × 4 = 32. ✔ Tip: For pie chart questions, always simplify the fraction first (part/whole) before multiplying by 360°. This keeps the numbers small and reduces calculation errors. Also, you can quickly sanity-check: 72 is under 10% of 810 (about 8.9%), so the angle should be under 36°. Only option A fits.

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