Question 29

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Jambmaths question: 

If the angle of a sector of a circle with radius 10.5cm is 120o, find the perimeter of the sector

Option A: 

45cm

Option B: 

48cm

Option C: 

40cm

Option D: 

43cm

Jamb Maths Solution: 

$\begin{align}  & \text{Length of the arc}=\frac{\theta }{{{360}^{\circ }}}\times 2\pi r \\ & r=10.5cm=\frac{21}{2}cm \\ & l=\frac{{{120}^{\circ }}}{{{360}^{\circ }}}\times 2\times \frac{22}{7}\times \frac{21}{2} \\ & l=22cm \\ & \text{Perimeter of the sector}=p=l+2r \\ & p=[22+2(10.5)]cm=43cm \\\end{align}$

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