PSLE A symmetric figure is drawn on a rectangular piece of paper 20 cm by 15 cm as shown. Its outline consists of a large semicircle, 2 smaller semicircles and 2 straight lines.
- What is the area of the figure?
- What is its perimeter? Take π = 3.14
(a)
Radius of the large semicircle
= 20 ÷ 2
= 10 cm
Area of the large semicircle
=
12 x 3.14 x 10 x 10
= 157 cm
2 Breadth of the small rectangle
= 15 - 10
= 5 cm
Area of the small rectangle
= 20 x 5
= 100 cm
2 Area of the 2 smaller semicircles
= 3.14 x 5 x 5
= 78.5 cm
2 Area of the 4 boomerangs
= 100 - 78.5
= 21.5 cm
2 Area of the figure
= 21.5 + 157
= 178.5 cm
2 (b)
Circumference of the curved lines
= 3.14 x 20
= 62.8 cm
Perimeter of the figure
= 62.8 + 5 + 5
= 72.8 cm
Answer(s): (a) 178.5 cm
2; (b) 72.8 cm