Perimeter of Rectangles

Perimeter of a Rectangle

The perimeter is the total distance around the outside of a shape. For a rectangle, opposite sides are equal, so there are two lengths and two widths.

1) Use the rectangle rule

If the length is (l) and the width is (w), then [ P = l + w + l + w = 2l + 2w = 2(l+w). ] Pick the form that is easiest for the numbers in the problem.

2) Substitute the given values

Write the length and width exactly as given, then add them.

• First find (l+w)
• Then multiply by 2

3) Simplify carefully

Carry out the arithmetic and reduce the result if needed. If the answer is in a unit, keep the unit consistent, such as cm, m, or in.

4) Check your answer

A quick check is to make sure the perimeter is larger than either side length and equals the sum of all four sides. You can verify by adding all sides directly: (l+w+l+w).

Example method

If you see dimensions, always identify which side is the length and which is the width before substituting. Then compute the total around the shape, not the area.