The length of a rectangle is five times its width. if the area of the rectangle is 125 m2 , find its perimeter.

L = length 
W = width

L = 5W      Length is 5 times the width
A = LW= 125

first lets find L and W 

A = LW = 125LW is the formula for area of a rectangle
 we know L = 5W 
we'll plug in 5W for L
A = (5W)W = 125
A = 5W^2 = 125
W^2 = 125/5
W^2 = 25
Take the squareroot 
W = 5

L = 5W
L = 5 * 5
L = 25

P = Perimeter = 2(L + w)  formula for perimeter of a rectangle
P = 2(25 + 5)
P = 60