PSLE A symmetric figure is drawn on a rectangular piece of paper 216 cm by 135 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
= 216 ÷ 2
= 108 cm
Area of the large semicircle
=
12 x 3.14 x 108 x 108
= 18312.48 cm
2 Breadth of the small rectangle
= 135 - 108
= 27 cm
Area of the small rectangle
= 216 x 27
= 5832 cm
2 Area of the 4 smaller semicircles
= 2 x 3.14 x 27 x 27
= 4578.12 cm
2 Area of the 8 boomerangs
= 5832 - 4578.12
= 1253.88 cm
2 Area of the figure
= 1253.88 + 18312.48
= 19566.36 cm
2 (b)
Circumference of the curved lines
= 3.14 x 216
= 678.24 cm
Perimeter of the figure
= 678.24 + 27 + 27
= 732.24 cm
Answer(s): (a) 19566.36 cm
2; (b) 732.24 cm