PSLE A symmetric figure is drawn on a rectangular piece of paper 144 cm by 96 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
= 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
= 96 - 72
= 24 cm
Area of the small rectangle
= 144 x 24
= 3456 cm
2 Area of the 3 smaller semicircles
= 1.5 x 3.14 x 24 x 24
= 2712.96 cm
2 Area of the 6 boomerangs
= 3456 - 2712.96
= 743.04 cm
2 Area of the figure
= 743.04 + 8138.88
= 8881.92 cm
2 (b)
Circumference of the curved lines
= 3.14 x 144
= 452.16 cm
Perimeter of the figure
= 452.16 + 24 + 24
= 500.16 cm
Answer(s): (a) 8881.92 cm
2; (b) 500.16 cm