PSLE A symmetric figure is drawn on a rectangular piece of paper 108 cm by 81 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
= 108 ÷ 2
= 54 cm
Area of the large semicircle
=
12 x 3.14 x 54 x 54
= 4578.12 cm
2 Breadth of the small rectangle
= 81 - 54
= 27 cm
Area of the small rectangle
= 108 x 27
= 2916 cm
2 Area of the 2 smaller semicircles
= 3.14 x 27 x 27
= 2289.06 cm
2 Area of the 4 boomerangs
= 2916 - 2289.06
= 626.94 cm
2 Area of the figure
= 626.94 + 4578.12
= 5205.06 cm
2 (b)
Circumference of the curved lines
= 3.14 x 108
= 339.12 cm
Perimeter of the figure
= 339.12 + 27 + 27
= 393.12 cm
Answer(s): (a) 5205.06 cm
2; (b) 393.12 cm