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 

Answer 1

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`