The length of a rectangle is three times its width. If the perimeter of the rectangle is 80ft., what is its length and width.

Answer 1

Let's assume L is the width of the rectangle and W is the width. Turning the two pieces of information into mathematical equations, for the first one we have the length is three times the width, therefore

L = 3*W

and the second information is that the perimeter is 80ft, therefore,

80 ft = 2*L + 2*W

the numbers L and W that are unknown to us now and we are trying to find them should meet the two equations above. Using the first equation and replacing L with 3*W in the second equation we get:

80 ft = 2*(3*W) + 2*W = 8*W

Therefore,

80 ft = 8*W

and thus we have

W = 10 ft

now the value of W can be used to calculate L using any of the two equations. Since the first one is simpler we use that

L = 3*W = 3*10 ft = 30 ft

L = 30 ft