PSLE A symmetric figure is drawn on a rectangular piece of paper 144 cm by 90 cm as shown. Its outline consists of a large semicircle, 4 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
= 144 ÷ 2
= 72 cm
Area of the large semicircle
=
12 x 3.14 x 72 x 72
= 8138.88 cm
2 Breadth of the small rectangle
= 90 - 72
= 18 cm
Area of the small rectangle
= 144 x 18
= 2592 cm
2 Area of the 4 smaller semicircles
= 2 x 3.14 x 18 x 18
= 2034.72 cm
2 Area of the 8 boomerangs
= 2592 - 2034.72
= 557.28 cm
2 Area of the figure
= 557.28 + 8138.88
= 8696.16 cm
2 (b)
Circumference of the curved lines
= 3.14 x 144
= 452.16 cm
Perimeter of the figure
= 452.16 + 18 + 18
= 488.16 cm
Answer(s): (a) 8696.16 cm
2; (b) 488.16 cm