Question

the radii of two right circular cylinders are in the ratio 2:3 and their heights are in the ratio 5:4 then find the ratio of their curved surface areas
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Answer 1

Answer:

Let the radii of 2 cylinders be 2r and 3r respectively and their heights be 5h and 4h respectively.

Let S1

and S2

be the curved surface areas of two cylinders.

S1

→ CSA of cylinder of radius 2r and height 5h=S1

=2×π×2r×5h=20πrh

S2

→ CSA of cylinder with radius 3r and height 4h=S2

=2×π×3r×4h=24πrh

∴

S2

S1

=

24πrh

20πrh

=

65

∴S1

:S2

=5:6.