If the height of a cylinder is doubled and radius remains the same, then volume will be
(a) doubled
(b) halved          
(c)  same  
(d)  four times

Explanation

let radius `=r`

and height `=h`

so volume `v=pixx(r^2)h`

in new case radius `R=r`

height `H=2h`
so new volume `V=pixx(r)^2(2h)`

`=2xx[pixx(r^2)h]`

`=2v`
so ans is a) doubled