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Question
Mark the correct alternative in each of the following:
In a cylinder, if radius is doubled and height is halved, curved surface area will be
Options
halved
doubled
same
four times
Solution
Let S1 be the curved surface area of the cylinder with radius r1 and height h1, then
`S_1 = 2pir_1h_1`……. (1)
Now, let S2 be the surface area after changing the dimension, then
`r_2 = 2r_1,h_2=h_1/2`
So,
`S_2 = 2pir_2h_2 = 2pi xx 2r_1xxh_1/2`
`⇒ S_2 = 2pir_1h_1 = S_1`
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