PSLE A symmetric figure is drawn on a rectangular piece of paper 160 cm by 100 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
= 160 ÷ 2
= 80 cm
Area of the large semicircle
=
12 x 3.14 x 80 x 80
= 10048 cm
2 Breadth of the small rectangle
= 100 - 80
= 20 cm
Area of the small rectangle
= 160 x 20
= 3200 cm
2 Area of the 4 smaller semicircles
= 2 x 3.14 x 20 x 20
= 2512 cm
2 Area of the 8 boomerangs
= 3200 - 2512
= 688 cm
2 Area of the figure
= 688 + 10048
= 10736 cm
2 (b)
Circumference of the curved lines
= 3.14 x 160
= 502.4 cm
Perimeter of the figure
= 502.4 + 20 + 20
= 542.4 cm
Answer(s): (a) 10736 cm
2; (b) 542.4 cm