PSLE A symmetric figure is drawn on a rectangular piece of paper 80 cm by 60 cm as shown. Its outline consists of a large semicircle, 2 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
= 80 ÷ 2
= 40 cm
Area of the large semicircle
=
12 x 3.14 x 40 x 40
= 2512 cm
2 Breadth of the small rectangle
= 60 - 40
= 20 cm
Area of the small rectangle
= 80 x 20
= 1600 cm
2 Area of the 2 smaller semicircles
= 3.14 x 20 x 20
= 1256 cm
2 Area of the 4 boomerangs
= 1600 - 1256
= 344 cm
2 Area of the figure
= 344 + 2512
= 2856 cm
2 (b)
Circumference of the curved lines
= 3.14 x 80
= 251.2 cm
Perimeter of the figure
= 251.2 + 20 + 20
= 291.2 cm
Answer(s): (a) 2856 cm
2; (b) 291.2 cm