Review of Plane Figures: Rectangles and Squares

Vocabulary

Plane Figure: a 2-dimensional quadrilateral. (It’s a flat shape)

Perimeter: the distance around a plane figure. You can find the perimeter of a figure by adding the lengths of its sides.

Problem

The security guard checks the perimeter of the rectangular building every morning. If its length is 100 feet, and its width is 75 feet, what is the perimeter of the building?

Strategy

You can use formulas to find the perimeters of rectangles and squares.

Perimeter of a Rectangle

P = 2 l + 2 w

Perimeter of a Square

P = 4 s

Solution

If P = 2 l + 2 w , then

P — 2(100) + 2(50) = 300 feet

The perimeter of the building is 300 feet.

Examples

Practice

Find the perimeter or missing measurement for each shape.

Math Challenge

Complete the table.

Each figure is a regular polygon with sides of 3 centimeters.

Answers

1.  14 in

2.  20 ft

3.  17.5 ft

4.  54 m

5.  14 yd

6.  6.7 m

7.  20 ft

8.  6 yd

Challenge.

pentagon:  3 + 3 + 3 + 3 + 3;  5 × 3;  15

hexagon:  3 + 3 + 3 + 3 + 3 + 3;  6 × 3;  18

octagon:   3 + 3 + 3 + 3 + 3 + 3 + 3 + 3;  8 × 3;  24