PSLE A symmetric figure is drawn on a rectangular piece of paper 180 cm by 120 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
= 180 ÷ 2
= 90 cm
Area of the large semicircle
=
12 x 3.14 x 90 x 90
= 12717 cm
2 Breadth of the small rectangle
= 120 - 90
= 30 cm
Area of the small rectangle
= 180 x 30
= 5400 cm
2 Area of the 3 smaller semicircles
= 1.5 x 3.14 x 30 x 30
= 4239 cm
2 Area of the 6 boomerangs
= 5400 - 4239
= 1161 cm
2 Area of the figure
= 1161 + 12717
= 13878 cm
2 (b)
Circumference of the curved lines
= 3.14 x 180
= 565.2 cm
Perimeter of the figure
= 565.2 + 30 + 30
= 625.2 cm
Answer(s): (a) 13878 cm
2; (b) 625.2 cm