PSLE A symmetric figure is drawn on a rectangular piece of paper 168 cm by 112 cm as shown. Its outline consists of a large semicircle, 3 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
= 168 ÷ 2
= 84 cm
Area of the large semicircle
=
12 x 3.14 x 84 x 84
= 11077.92 cm
2 Breadth of the small rectangle
= 112 - 84
= 28 cm
Area of the small rectangle
= 168 x 28
= 4704 cm
2 Area of the 3 smaller semicircles
= 1.5 x 3.14 x 28 x 28
= 3692.64 cm
2 Area of the 6 boomerangs
= 4704 - 3692.64
= 1011.36 cm
2 Area of the figure
= 1011.36 + 11077.92
= 12089.28 cm
2 (b)
Circumference of the curved lines
= 3.14 x 168
= 527.52 cm
Perimeter of the figure
= 527.52 + 28 + 28
= 583.52 cm
Answer(s): (a) 12089.28 cm
2; (b) 583.52 cm