Question

If the length of the radius of a right circular cylinder is doubled and height is halved, then its lateral surface area will be
A. equal
B. double
C. half
D. 3 times

Answer 1

Correct Answer - A
Let the radius of the cylinder be r units and height of it be h units.
`:.` the lateral surface area `= 2 pi rh ` sq-units
If the radius is doubled, i.e., 2r units and the height is halved, i.e., `h/2` units, then the lateral surface area becomes `2 pi xx 2r xx h/2 sq - "units" = 2pi r h ` sq-units.
`:.` The lateral surface area remains the same , i.e., in both the cases the lateral surface areas are equal.
`:.` (a) is correct.