Discussion
The radii of two right circular cylinders are in the ratio 4:3 and their heights are in the ratio 7:4 then the ratio of their curved surface areas is in the ratio
Answer: D
The ratio of the curved surface areas is 7 : 3.
The curved surface area of a cylinder is \(2\pi r h\), so the ratio is the product of the radius ratio and the height ratio:
\[ \begin{aligned} \frac{S_{1}}{S_{2}} &= \frac{4}{3} \times \frac{7}{4} \\ &= \frac{28}{12} = \frac{7}{3} \end{aligned} \]
3 : 7 is the same ratio inverted. 5 : 3 and 3 : 5 do not come from these figures; squaring the radius ratio, as for volume, would also be a mistake here.
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