Perimeter of rectangle as a Variable

A Rectangle has 4 sides

and opposite sides of a Rectangle are equal.

Let AB = l & BC = b

So, CD = AB = l

  & AD = BC = b

Thus,

  Perimeter = Sum of all sides

           = AB + BC + CD + AD

           = l + b + l + b

           = 2 l + 2b

           = 2( l + b)

So we can write,

Perimeter of rectangle = 2( l + b)

    where l is length and b is width of rectangle