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JAMB Mathematics 2013 Paper

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Question : 40

Total: 47

A chord of a circle subtends an angle of 120° at the centre of a circle of diameter

4\sqrt{3}\,\text{cm}

. Calculate the area of the major sector.

32 $\pi$ cm $^2$
4 $\pi$ cm $^2$
8 $\pi$ cm $^2$
16 $\pi$ cm $^2$

Solution:

Angle of major sector = 360° - 120° = 240°

Area of major sector : $\frac{\theta}{360} \times \pi r^{2}$

r = $\frac{4\sqrt{3}}{2} = 2\sqrt{3}\,\text{cm}$

Area : $\frac{240}{360} \times \pi \times (2\sqrt{3})^{2}$

= $8\pi\,\text{cm}^{2}$

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