Since the fort is 6 feet long and six feet tall on all sides, the floor, the ceiling, and four walls are all 6 ft by 6ft. Each one then has an area of 6x6=36. The total he has to paint is then 6x36=216 square ft. Since each bucket covers 300 square ft and he has less than 300 square ft to paint, makes him only need one bucket of paint.
