WAEC 2019 · Paper 1 · Q25

Plane mensuration

An arc subtends an angle of $72^\circ$ at the centre of a circle. Find the length of the arc if the radius of the circle is $3.5\text{ cm}$ . $\left[\text{Take }\pi = \frac{22}{7}\right]$

Worked solution (try it first)

The circumference is $2 \times \frac{22}{7} \times 3.5 = 22$ cm.
The arc is $\frac{72}{360} = \frac15$ of it: $22 \div 5 = 4.4$ cm, option C.

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