PSLE A symmetric figure is drawn on a rectangular piece of paper 80 cm by 50 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
= 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
= 50 - 40
= 10 cm
Area of the small rectangle
= 80 x 10
= 800 cm
2 Area of the 4 smaller semicircles
= 2 x 3.14 x 10 x 10
= 628 cm
2 Area of the 8 boomerangs
= 800 - 628
= 172 cm
2 Area of the figure
= 172 + 2512
= 2684 cm
2 (b)
Circumference of the curved lines
= 3.14 x 80
= 251.2 cm
Perimeter of the figure
= 251.2 + 10 + 10
= 271.2 cm
Answer(s): (a) 2684 cm
2; (b) 271.2 cm