PSLE A symmetric figure is drawn on a rectangular piece of paper 40 cm by 30 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
= 40 ÷ 2
= 20 cm
Area of the large semicircle
=
12 x 3.14 x 20 x 20
= 628 cm
2 Breadth of the small rectangle
= 30 - 20
= 10 cm
Area of the small rectangle
= 40 x 10
= 400 cm
2 Area of the 2 smaller semicircles
= 3.14 x 10 x 10
= 314 cm
2 Area of the 4 boomerangs
= 400 - 314
= 86 cm
2 Area of the figure
= 86 + 628
= 714 cm
2 (b)
Circumference of the curved lines
= 3.14 x 40
= 125.6 cm
Perimeter of the figure
= 125.6 + 10 + 10
= 145.6 cm
Answer(s): (a) 714 cm
2; (b) 145.6 cm