JAMB 1994 · UME · Q30

Plane mensuration

Calculate the perimeter, in cm, of a sector of a circle of radius 8 cm and angle $45^\circ$ .

Worked solution (try it first)

The circumference is $2\pi \times 8 = 16\pi$ cm.
The arc is $\frac{45}{360} = \frac18$ of it: $\frac18 \times 16\pi = 2\pi$ cm.
The perimeter adds both radii: $8 + 8 + 2\pi = 16 + 2\pi$ cm, option C.

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