confused about math

Question

The length of a rectangle is three times it’s width. If the perimeter of the rectangle is 80 m, what’s the area

Answer 1

Let:

l be the length of the side of the rectangle and

w be the width.

We know the length is three times the width:

l = 3w.

The perimeter is the sum of all sides of the rectangle

P = l + w + l + w

P = 3w + w + 3w + w

P = 8w.

We substitute P with 80 and solve for w:

80 = 8w

w = 10m.

We find the length:

l = 3w

l = 30m.

The area is

A = lw

A = 30x10

A =300 sq.m.

The area of the rectangle is 300 sq. meters.