PSLE A symmetric figure is drawn on a rectangular piece of paper 72 cm by 45 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
= 72 ÷ 2
= 36 cm
Area of the large semicircle
=
12 x 3.14 x 36 x 36
= 2034.72 cm
2 Breadth of the small rectangle
= 45 - 36
= 9 cm
Area of the small rectangle
= 72 x 9
= 648 cm
2 Area of the 4 smaller semicircles
= 2 x 3.14 x 9 x 9
= 508.68 cm
2 Area of the 8 boomerangs
= 648 - 508.68
= 139.32 cm
2 Area of the figure
= 139.32 + 2034.72
= 2174.04 cm
2 (b)
Circumference of the curved lines
= 3.14 x 72
= 226.08 cm
Perimeter of the figure
= 226.08 + 9 + 9
= 244.08 cm
Answer(s): (a) 2174.04 cm
2; (b) 244.08 cm