Q7 of 79 Page 229

The radii of two right circular cylinders are in the ratio of 3 : 2 and their heights are in the ratio 5 : 3. Find the ratio of their curved surface areas.

Given : Ratio of radii of two cylinders = r1 : r2 = 3 : 2

Ratio of heights of the two cylinders = h1 : h2 = 5 : 3


To find : Ratio of CSA of the two cylinders = C1 : C2 = ?


Formula : CSA of cylinder = 2rh


Solution : CSA of first cylinder = C1 = 2r1h1


CSA of first cylinder = C2 = 2r2h2


∴


⇒


∴ C1 : C2 = 5 : 2


∴ The ratio of the curved surface areas of the two cylinders is 5 : 2.


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