Page 346 - Math Smart - 7

Solution
a) Perimeter =15 + 12 + 3 + 4 + 12 + 8
= 54 cm
b) There are two methods to calculate the area of this compound shape.

Method 2
Method 1
Divide the compound shape into rectangles using Draw dotted lines to form a complete
dotted lines. There is more than one way to do this. rectangle.

15 cm 15 cm
< >■ < ►

cm 8 cm
12 cm 12 cm

12 cm 12 cm
4 cm
'■3
3 cm 3 cm

Calculate the area of each rectangle. Calculate the area of the rectangle formed.
Then find the sum of the areas. Subtract the area of the unshaded rectangle.
15 cm
15 cm

8 cm
12 cm 12 cm

12 cm

3 cm
12 cm
Area of rectangle A = 15 x 8
= 120 cm^ 4 cm
Area of rectangle B = 4 x 3

= 12 cm^ Area of rectangle A = 15 x 12
Area of composite figure = 120 + 12 =180cm^

=132cm^ Area of rectangle B = 4 x 12
= 48 cm^

Area of composite figure = 180 - 48
= 132 cm^

3^ UNIT 15 Measuring Time, Area, Perimeter and Volume