The north wall of a barn is a rectangle 25 feet high and 60 feet long. There are five windows in the wall, each 8 by 10 feet. If a gallon of paint will cover 275 ft2, how many gallons of paint must the painter buy to paint the wall?

(25 * 60) - (5 * 8 * 10) =

Divide the answer by 275.

To determine the amount of paint needed to paint the wall, we need to calculate the area of the wall first.

The area of a rectangle can be found by multiplying its length by its width. In this case, the length of the wall is given as 60 feet and the height is given as 25 feet. Therefore, the area of the entire wall can be calculated as:

Area of the wall = Length × Height
Area of the wall = 60 ft × 25 ft
Area of the wall = 1500 ft²

Now, let's calculate the area of the five windows. The dimensions of each window are given as 8 feet by 10 feet. So, the area of one window is:

Area of one window = Length × Height
Area of one window = 8 ft × 10 ft
Area of one window = 80 ft²

Since there are five windows, we need to multiply the area of one window by five to get the total area of all the windows:

Total area of the windows = Area of one window × Number of windows
Total area of the windows = 80 ft² × 5
Total area of the windows = 400 ft²

To find the area of the wall that needs to be painted, we subtract the total area of the windows from the total area of the wall:

Area to be painted = Area of the wall - Total area of the windows
Area to be painted = 1500 ft² - 400 ft²
Area to be painted = 1100 ft²

Now, we can calculate the number of gallons of paint needed, knowing that one gallon will cover 275 ft²:

Number of gallons of paint needed = Area to be painted ÷ Coverage per gallon
Number of gallons of paint needed = 1100 ft² ÷ 275 ft²/gallon
Number of gallons of paint needed = 4 gallons

Therefore, the painter must buy 4 gallons of paint to paint the wall.