Learning Target: I can fluently compute the perimeter rectangles and squares.

Review of Rectangles and Squares

Plane Figure: a 2-dimensional shape. (in other words, 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.

Example 1

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?

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

If P = 2 l + 2 w , then

P = 2(100) + 2(50) = 300 feet

The perimeter of the building is 300 feet.

Example 2

Example 3

Let's Practice Together

Find the perimeter or missing measurement for each shape.

Your Turn

Check for Understanding

1.  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

Check for Understanding

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