JAMB 2017 · UTME (set 2) · Q4

The curved surface area of a cylinder $5\text{ cm}$ high is $110\text{ cm}^2$ . Find the radius of its base. $\left[\pi = \frac{22}{7}\right]$

Worked solution (try it first)

Curved surface area of a cylinder is $2\pi rh$ : $2 \times \frac{22}{7} \times r \times 5 = 110$ .
That is $\frac{220}{7}r = 110$ , so $r = 110 \times \frac{7}{220} = 3.5$ cm, option B.