PSLE A symmetric figure is drawn on a rectangular piece of paper 32 cm by 20 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
= 32 ÷ 2
= 16 cm
Area of the large semicircle
=
12 x 3.14 x 16 x 16
= 401.92 cm
2 Breadth of the small rectangle
= 20 - 16
= 4 cm
Area of the small rectangle
= 32 x 4
= 128 cm
2 Area of the 4 smaller semicircles
= 2 x 3.14 x 4 x 4
= 100.48 cm
2 Area of the 8 boomerangs
= 128 - 100.48
= 27.52 cm
2 Area of the figure
= 27.52 + 401.92
= 429.44 cm
2 (b)
Circumference of the curved lines
= 3.14 x 32
= 100.48 cm
Perimeter of the figure
= 100.48 + 4 + 4
= 108.48 cm
Answer(s): (a) 429.44 cm
2; (b) 108.48 cm