Cylinder

The cylinder surface is 139 dm2, its height is equal to the radius of the base. Calculate height of this cylinder.

Result

h =  3.3 dm

Solution:

$$S = 2 \pi r^2 + 2 \pi r h = 4 \pi r^2 \\~\\h = r = \sqrt{ \frac{ 139 }{ 4 \pi}} = 3.3 \ \text { dm }$$