Question

if 1 gallon of paint covers 400 sq feet, about how many gallons of paint are needed to paint the outside of a spherical tank of diameter 20 feet?

Answer 1

`diameter\ d=20ft;\ d=2r\ (r-radius)\\\\2r=20ft\to r=10ft\\\\Surface\ area\ of\ the\ a\ spherical\ tank:A=4\pi r^2\\\\A=4\pi(10^2)=400\pi\approx400*3.14=1256\ (ft^2)\\\\\\1256:400=3.14\\\\Answer:Needed\ more\ than\ 3\ gallons\ of\ paint\ (\approx3.15\ gallons).`