An acre is a unit of measure for area. One acre ie equal to 43,560 square feet. Often, an acre is a rectangle that measures 660 feet by 66 feet. However, the length and width of the rectangle can vary. An acre can actually have any shape, as long as it measures exactly 43,560 square feet. Rachel purchased 1/5 acre of land in the shape of an isosceles triangle. What is the area of the land Rachel purchased?