How many gallons of seal are needed for two coats on a retaining wall measuring 400' by 20' if one gallon covers 255 square feet?

To determine the correct amount of seal needed for two coats on a retaining wall measuring 400 feet by 20 feet, first calculate the total area of the wall. The area is found by multiplying the length by the height, resulting in an area of 400 feet x 20 feet, which equals 8,000 square feet.

Since the application requires two coats, the total area to be covered doubles: 8,000 square feet x 2 = 16,000 square feet.

Given that one gallon of seal covers 255 square feet, to find out how many gallons are necessary for 16,000 square feet, divide the total area by the coverage per gallon: 16,000 square feet ÷ 255 square feet per gallon = approximately 62.75 gallons.

This calculation confirms that option B, which states 62.75 gallons, is the correct amount needed for sealing the retaining wall with two coats.