You know that the area of a square is length times width. There are two possible combinations of whole numbers: 1 x 25 and 5 x 5. A square is equal on all sides, so the both the length and the width have to be 5. To find the answer, a square has 4 sides, and 4 x 5 (or 5 + 5+ 5+ 5) equals 20.
