WAEC 2025 · Paper 1 · Q32✱✱

A sector has angle $108^\circ$ and radius $3\frac12\text{ cm}$ . Find its perimeter. $\left[\pi = \frac{22}{7}\right]$

Worked solution (try it first)

Arc length $= \frac{108}{360} \times 2 \times \frac{22}{7} \times 3.5$ .
The circumference is 22 cm, and $\frac{108}{360} = \frac{3}{10}$ , so the arc is $6.6$ cm.
The perimeter adds the two radii: $6.6 + 2 \times 3.5 = 13.6 = 13\frac35$ cm, option D.