Ratio of width to length: W/L = 3/5
5W = 3L .........(a)
Perimeter = 2*(L+W) = 80
2*(L+W) = 80
(L+W) = 80/2. Divide both sides by 2.
L+W= 40......(b)
5W = 3L
L + W = 40 Multiply both sides by 5.
5*(L+W) = 5*40
5L+5W = 200. Recall from (a) 5W = 3L
5L + 3L = 200
8L = 200
L = 200/8
L = 25.
5W = 3L
5W = 3*25
W = 3*25/5
W = 15.
Therefore, the length, L = 25 and width , W = 15.