10.12 Perimeter and area

Lesson

Practice

Lesson

Are you ready?

Let's review how to find the perimeter and how to find the area of a rectangle.

Find the perimeter of the rectangle shown.

Find the area of the rectangle shown.

	width = $2$2 $cm$
length = $12$12 $cm$

$\text{Area }$Area	$=$=	$\text{length }\times\text{width }$length ×width	$cm$ ²
$\text{Area }$Area	$=$=	$\editable{}\times\editable{}$×	$cm$ ²	(Fill in the values for the length and width.)
$\text{Area }$Area	$=$=	$\editable{}$	$cm$ ²	(Complete the multiplication to find the area.)

Learn

You may have noticed already that shapes with the same perimeter don't always have the same area, as shown in the rectangles below. Similarly, shapes with the same area don't always have the same perimeter.

This video looks at the relationship between perimeter and area.

Apply

Which of these rectangles has an area of $24$24 cm² and a perimeter of $20$20 cm?

(Note: Diagrams are not to scale.)

$2$2 cm

$5$5 cm

A

$4$4 cm

$6$6 cm

B

$3$3 cm

$7$7 cm

C

$3$3 cm

$8$8 cm

D

Remember!

Rectangles can have the same perimeter and have different areas.

Outcomes

3.MD.C.8

Solve real-world and mathematical problems involving perimeters of plane figures and areas of rectangles, including finding the perimeter given the side lengths, finding an unknown side length. Represent rectangles with the same perimeter and different areas or with the same area and different perimeters.