Volume of a cylinder=πr2h where h is the height and r the radius.
Surface area=2πrh.
If the volume is V, then r2=V/(πh) and r=√(V/(πh)).
Therefore the surface area S=2πh√(V/(πh))=2√(Vπh). Since V and h are known and π=3.142 approx, S can be calculated.
EXAMPLE
If V=1000cm3 (1 litre) and h=10cm then 1000=10πr2, so r=10/√π cm=5.642cm approx.
S=2πrh=112.84π=354.49cm2 approx.
S=2√Vπh=2√10000π=200√π=354.49cm2, using the formula S=2√(Vπh).