Objectives:

Vocabulary:

• Deduce and use formula for the perimeter and area of a rectangle.

• Calculate the perimeter and area of shapes made from rectangles.

The area of this rectangle is 12 cm².

What are the possible dimensions – length and width of this rectangle?

Which of the rectangles you have found has the largest perimeter?

Possible answers 1 x 12 cm 2 x 6 cm 3 x 4 cm

(any other answers would involve lengths with decimals).

Largest perimeter 1 x 12 cm rectangle with a perimeter of 26cm.

Even greater perimeters are achieved if decimal lengths are acceptable!!!

( Example 0.1 x 120cm perimeter is 240.2cm.)

This rectangle has a perimeter of 12 cm.

Find as many different rectangles with a perimeter of 12cm.

Which of the rectangles has the largest area?

Possible answers: 4 x 2 cm, 3 x 3 cm, 1 x 5 cm

Any other answers would include decimal lengths.

Largest area: 3 x 3 cm = 9cm²

8cm6c

m

3cm

5cm

Work out the area and perimeter of the shape.

8cm

6cm

3cm

5cm

A

B

Area is:

A + B

Perimeter: 6 + 8 + 3 + 3 + 3 + 5cm

8cm

6cm

Area is: -

Perimeter: Why?

3cm

3cm

Find the area and perimeter of each of the shapes below: (all measurements given in cms)

5 8

9

3

4

4

3

8

5

2

7

2

4

3

10

4

7

5

W/S 9.1B

Answers:

5 8

9

3

4

4

3

8

5

2

7

2

4

3

10

4

7

5

A = 47 cm²

P = 34 cm

A = 40 cm²

P = 30 cm

A = 32 cm²

P = 32 cm

A = 75 cm²

P = 38 cm

15m

10m

3m

3m

Calculate the area shaded green.

Working:

(15 x 10) – (3 x 3) = 150 – 9 = 141m²

60cm

40cm

10cm

10cm

Calculate the area of the blue cross.

Working:

(10 x 60) + (10 x 40) – (10 x 10)

600 + 400 - 100 = 900cm²

W/S 9.2B

Objectives:

Vocabulary:

• Deduce and use formula for the perimeter and area of a rectangle.

• Calculate the perimeter and area of shapes made from rectangles.

Thank you for your attention