. "You can use the formula: P = 2l + 2w where P is the perimeter of the rectangle, l is the length of the rectangle, and w is the width of the rectangle to find the perimeter of a rectangle. Derivation: Simply adding up the lengths of the sides: P = l + w + l + w = 2l + 2w"@en . . "You can use the formula: P = 2l + 2w where P is the perimeter of the rectangle, l is the length of the rectangle, and w is the width of the rectangle to find the perimeter of a rectangle. Derivation: Simply adding up the lengths of the sides: P = l + w + l + w = 2l + 2w"@en . "How do you find the perimeter of a rectangle"@en .