The greatest length will be the length and the breadth.
Perimeter is 2 * (l + b)
2 * (4b + b) = 170 (length is 4 times breadth)
2 * 5b = 170
5b = 170/2 = 85
b = 85 / 5 = 17
l = 4b
l = 4 * 17 = 68
So the largest possible dimensions are [tex]68 * 17 cm[/tex] :D
