Page 175 - Mathematics Coursebook

18.3 Calculating the area and perimeter of compound shapes

2 Work out the area and perimeter of each of these compound shapes.
a b

6 cm
6 cm
6 cm
3 cm 6 cm 8 cm
3 cm
8 cm
3 cm
8 cm
9 cm 3 cm 8 cm
9 cm
9 cm
9 cm
4 cm 13 cm
4 cm
13 cm
4 cm 13 cm
13 cm
4 cm
1 cm
1 cm
1 cm
1 cm
10 cm
10 cm
10 cm
10 cm
12 mm
5 m
12 mm
5 m
c 5 m d 12 mm
12 mm
5 m
20 mm
20 mm
20 mm
20 mm
15 mm
15 mm
4 m 15 mm
4 m
15 mm
4 m
4 m
10 mm
10 mm
10 mm
1 m 10 mm
1 m
1 m
1 m
4 m
4 m
4 m
4 m

3 Copy and complete the workings to find the area of the blue section in this diagram.
2
Area of large rectangle = 30 × = cm 30 cm
Area of hole = 8 × = cm 2 8 cm
Blue area = – = cm 2 10 cm 4 cm
4 Work out the area of the red section in each of these diagrams.
a 9 cm b 50 cm
50 cm
9 cm
2 cm
2 cm
9 cm 30 cm
9 cm
30 cm
8 cm 20 cm
8 cm
20 cm
6 cm
6 cm
5 cm
12 cm 5 cm
12 cm
5 T his is par t o f V ishanthan ’ s ho me w o r k.
5 This is part of Vishanthan’s homework.
Question Work out the area and perimeter of this compound shape.
Solution Area A = 5 × 8 = 40 FP
Area B = 6 × 4 = 24
Area C = 20 × 1 = 20 FP $ FP FP
Total area = 40 + 24 + 20 = 84 cm % FP
Perimeter = 10 + 5 + 8 + 6 + 4 &
+ 20 = 53 cm 2 FP
Vishanthan has made several mistakes.
Explain what he has done wrong. Work out the correct answers for him.
174 18 Area, perimeter and volume