The base radii of two cylinders are in the ratio 4 : 5 and their heights are in the ratio 2 : 9. The ratio of their curved surface areas is:
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → 8 : 45
The curved surface area of a cylinder is \(2\pi rh\), so the ratio of two such areas is the ratio of the radii times the ratio of the heights (\(2\pi\) cancels).
Ratio of the curved surface areas \(\displaystyle=\frac{2\pi r_1h_1}{2\pi r_2h_2}=\frac{4}{5}\times\frac{2}{9}=\frac{8}{45}\)