Objectives Calculate the area and perimeter of shapes

Objectives: • Calculate the area and perimeter of shapes made from rectangles. • Know and use the formula for calculating the area of a rectangle. Vocabulary: cm 2 cm

Perimeter 1 cm 1 cm

4 cm 1 cm 4 cm Perimeter = 4 cm + 1 cm + 4 cm + 1 cm Perimeter = 10 cm

4 cm 2 cm 4 cm Perimeter = 4 cm + 2 cm + 4 cm + 2 cm Perimeter = 12 cm

5 cm 3 cm 5 cm Perimeter = 5 cm + 3 cm + 5 cm + 3 cm Perimeter = 16 cm

5 cm 3 cm Perimeter = 2 cm + 1 cm + 3 cm + 2 cm + 5 cm + 3 cm Perimeter = 16 cm

5 cm 3 cm Perimeter = 2 cm + 3 cm + 1 cm + 5 cm + 3 cm Perimeter = 16 cm

4 cm 2 cm 4 cm Perimeter = 3 cm + 1 cm + 3 cm + 1 cm Perimeter = 12 cm

4 cm Perimeter = 4 cm + 1 cm + 2 cm + 1 cm + 3 cm + 4 cm Perimeter = 20 cm

4 cm 2 cm ? cm 3 cm 2 cm ? cm 5 cm

4 cm 2 cm 5 cm 2 cm 3 cm Perimeter = 5 cm + 2 cm + 3 cm + 4 cm Perimeter = 18 cm

2 cm 6 cm ? cm 5 cm 3 cm ? cm

2 cm 6 cm 3 cm 5 cm 3 cm Perimeter = 6 cm + 2 cm + 3 cm + 5 cm Perimeter = 22 cm

a a Perimeter = a + a + a Perimeter = 4 x a Perimeter = 4 a

6 6 Perimeter = 6 + 6 + 6 Perimeter = 4 x 6 Perimeter = 24

a a a

a a 2 a Perimeter = 2 a + a Perimeter = 6 x a a

3 a a a 3 a Perimeter = 3 a + a Perimeter = 8 x a 8 a means 8 x a If a = 5 cm the perimeter = 8 x 5 = 40 cm

b a a b Perimeter = a + b + a + b Perimeter = 2 a + 2 b If a = 3 and b = 4 Perimeter = a + b + a + b Perimeter = 3 + 4 + 3 + 4 = 14 Perimeter = 2 a + 2 b Perimeter = (2 x 3) + (2 x 4) = 6 + 8 = 14

3 f 3 f Perimeter = 2 d + 3 f + 2 d + 3 f Perimeter = 4 d + 6 f Perimeter = (4 x 2) + (6 x 3) = 8 + 18 = 26 2 d 2 d d=2 f=3

4 g 2 m g=4 m=3 Perimeter = 2 m + 4 g + 2 m + 4 g Perimeter = 8 g + 4 m Perimeter = (8 x 4) + (4 x 3) = 32 + 12 = 44

c 5 a 2 c a= 7 c = 3 2 a c 3 a Perimeter = 5 a + c + 2 a + 3 a + 2 c Perimeter = 10 a + 4 c Perimeter = (10 x 7) + (4 x 3) = 70 + 12 = 82

Area 1 cm 1 cm 1 square cm 1 cm 2

5 cm 3 cm Area = 5 cm x 3 cm Area= 15 cm 2

6 cm 4 cm Area = 6 cm x 4 cm Area= 24 cm 2

3 cm Blue area = 3 cm x 3 cm = 9 cm 2 Yellow area = 6 cm x 1 cm = 6 cm 2 Total area 15 cm 2 4 cm 3 cm 6 cm

3 cm Red area = 3 cm x 4 cm = 12 cm 2 Green = 3 cm x 1 cm = 3 cm 2 Total area 15 cm 2 4 cm 3 cm 6 cm

4 cm 2 cm 3 cm Area= 14 cm 2 2 cm

6 cm 2 cm 4 cm 2 cm Area= 20 cm 2

6 cm 5 cm 4 cm Area= 26 cm 2

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 26 cm. Even greater perimeters are achieved if decimal lengths are acceptable!!! ( Example 0. 1 x 120 cm perimeter is 240. 2 cm. )

This rectangle has a perimeter of 12 cm. Find as many different rectangles with a perimeter of 12 cm. 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 = 9 cm²

8 cm 6 cm 3 cm Work out the area and perimeter of the shape. 5 cm 8 cm 6 cm B 3 cm 6 cm 3 cm A 5 cm Area is: Perimeter: - Area is: Why? A + B Perimeter: 6 + 8 + 3 + 3 + 5 cm

Find the area and perimeter of each of the shapes below: (all measurements given in cms) 9 8 W/S 9. 1 B 3 3 8 5 4 4 3 2 7 4 10 5 5 2 7 4

Answers: 9 8 3 A = 40 cm² 3 P = 30 cm 8 5 A = 47 cm² 4 P = 34 cm 4 3 2 4 5 A = 75 cm² A = 32 cm² P = 32 cm P = 38 cm 10 5 2 7 4 7