The scale drawing uses a ratio of 2cm:1m. If the actual car is 4 meters long, you would multiply 2 by 4 to get 8cm. The actual new ratio on the map is 8cm:4m, which is equivalent to the one in the problem.
Area of each wall is 10*8 = 80 square feet there are 5 walls so total wall area is 5*80=400 he needs two coats on each wall so he needs to cover 2*400=800 square feet
