The perimeter of a rectangle is 40 cm. It’s length is 9 cm. What is it width?

Answer 1

A rectangle has 4 sides and each vertex is a right angle. That means that opposite sides have the same length. Let L be the length, and W be the width. The perimeter is just the sum of the lengths of the four sides:

P = L + W + L + W

or simply

P = 2(L+W)

We are told that P = 40 cm and L = 9 cm, so our equation now looks like

40 = 2(9 + W)

We need to solve for W:

9 + W = 40 / 2 = 20

W = 20 - 9 = 11

W = 11 cm