Measurement

NZ Level 3

Connecting Perimeters and Areas

Lesson

When we work with shapes, there are two important measurements we can use- perimeter and area.

When we calculate the perimeter of a shape, we need to work out how far it is around the outside of that shape. Let's work through some examples now.

When we calculate the area of a shape, we are looking at how much space is inside the shape. Let's look at how to calculate the area of our shapes.

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.

Let's look more at the relationship between perimeter and area now.

Remember!

Different rectangles can have the same perimeter. The rectangle with the largest area will be a square.

All shapes with the same perimeter have the same area.

Is this statement true or false?

True

AFalse

BTrue

AFalse

B

Which of these rectangles has an area of $24$24 cm^{2} and a perimeter of $28$28 cm?

(Note: Diagrams are not to scale.)

$2$2 cm $12$12 cm A$4$4 cm $10$10 cm B$4$4 cm $5$5 cm C$3$3 cm $8$8 cm D$2$2 cm $12$12 cm A$4$4 cm $10$10 cm B$4$4 cm $5$5 cm C$3$3 cm $8$8 cm D

Look at the picture of the rectangle and answer the following questions.

What is the area of this rectangle?

What is the perimeter of this rectangle?

Identify all the shapes that have the same perimeter as this rectangle. (Shapes not to scale)

ABCDABCD

Find areas of rectangles and volumes of cuboids by applying multiplication.