l = 105 cm; w = 21 cm
The formula for the perimeter of a rectangle is
P = 2(l+w)
We have the equations
(1) 2(l+w) = 252 cm
(2) l = 5w
Substitute Equation (2) into Equation (1):
2(5w + w) = 252 cm
2 × 6w = 12 w = 252 cm
w = 252 cm/12 = 21 cm
Substitute the value for w into Equation (2):
l = 5w = 5 × 21 cm = 105 cm