PSLE A symmetric figure is drawn on a rectangular piece of paper 120 cm by 80 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
= 120 ÷ 2
= 60 cm
Area of the large semicircle
=
12 x 3.14 x 60 x 60
= 5652 cm
2 Breadth of the small rectangle
= 80 - 60
= 20 cm
Area of the small rectangle
= 120 x 20
= 2400 cm
2 Area of the 3 smaller semicircles
= 1.5 x 3.14 x 20 x 20
= 1884 cm
2 Area of the 6 boomerangs
= 2400 - 1884
= 516 cm
2 Area of the figure
= 516 + 5652
= 6168 cm
2 (b)
Circumference of the curved lines
= 3.14 x 120
= 376.8 cm
Perimeter of the figure
= 376.8 + 20 + 20
= 416.8 cm
Answer(s): (a) 6168 cm
2; (b) 416.8 cm