As the rectangle has 4 sides and the length is three times the width, each pair of a long side and a short side has a perimeter of 18 meters. As the ratio is 3:1, there are 4 parts in 18 meters, and 18 divided by 4=4.5. As the length covers 3 parts, and there are 4.5 meters per part, 4.5x3=13.5. The length of the rectangle is 13.5 meters. Hope it helps!
