Hashem wants to put up fencing around three sides of his rectangular yard and leave a side of 20 feet unfenced. If the yard has an area of 680 square feet. How many feet of fencing does he need?

Since the yard is a rectangle and one side is 20, which we can call the length, then the width (w) is: 680 = 20w or, w = 34 Thus, he needs 34 + 34 + 20 = 88 feet of fencing. ans: 88 feet