1_(b) if the length is doubled, then there will be no change in the surface area as you can see the above formula for surface area in which there is no use of length.

2_(a) Height = 20 m Diameter = 15 m Radius = 15/2 m = 7.5 m

Surface area of the storage tanks = 2πrh+2πr^2 = 2(3.14)(7.5)(20) + 2(3.14)(7.5)^2 = 1295.25 ≈ 1295 m^2

2_(c) The area of 48 tanks that should be painted = 48 * 1295.25 = 62172 m^2

3_ Height = 50 + 2 + 2 mm = 54 mm Diameter = 26.2 mm Radius = 26.2 / 2 mm = 13.1 mm

The surface area of casing of the battery = 22766.49 mm^2 ≈ 22767 mm^2