If the radius of a cylinder is doubled and its height is halved, the CSA becomes:

If the radius of a cylinder is doubled and its height is halved, the CSA becomes:
  1. Same
  2. Doubled
  3. Halved
  4. Four times

Solution

New CSA $= 2\pi (2r)\left(\dfrac{h}{2}\right) = 2\pi r h$, i.e. unchanged.

Asked in: IMO

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