PSLE A symmetric figure is drawn on a rectangular piece of paper 140 cm by 105 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
= 140 ÷ 2
= 70 cm
Area of the large semicircle
=
12 x 3.14 x 70 x 70
= 7693 cm
2 Breadth of the small rectangle
= 105 - 70
= 35 cm
Area of the small rectangle
= 140 x 35
= 4900 cm
2 Area of the 2 smaller semicircles
= 3.14 x 35 x 35
= 3846.5 cm
2 Area of the 4 boomerangs
= 4900 - 3846.5
= 1053.5 cm
2 Area of the figure
= 1053.5 + 7693
= 8746.5 cm
2 (b)
Circumference of the curved lines
= 3.14 x 140
= 439.6 cm
Perimeter of the figure
= 439.6 + 35 + 35
= 509.6 cm
Answer(s): (a) 8746.5 cm
2; (b) 509.6 cm