3 gallons of paint is required to paint the building.
The area to be painted is:
= 2× [Area of Rectangle with dimensions 20 ft.×10 ft.+Area of triangle with height 5 ft. and base 20 ft.+Area of rectangle with dimensions 24 ft. and 10 ft.]
=2×[20×10+(1/2)×5×20+24×10]
=2×[200+50+240]
=2×490
=980 square ft.
Hence, the area to be painted=980 square feet.
Now, amount of paint require to cover 350 square feet=1 gallon.
i.e. 1 square feet requires=1/350 gallon of paint.
⇒ 980 square feet requires=980/350=2.8 gallons of paint.
Hence, to the nearest gallon we could say that:
3 gallons of paint is required to paint the building.
