WAEC 2025 · Paper 1 · Q26✱✱

A sphere has volume $k\text{ cm}^3$ and surface area $k\text{ cm}^2$ . Calculate its diameter.

Worked solution (try it first)

The volume and the surface area have the same number: $\frac43\pi r^3 = 4\pi r^2$ .
Divide both sides by $4\pi r^2$ : $\frac r3 = 1$ , so $r = 3$ cm.
The diameter is $2 \times 3 = 6$ cm, option D.