PSLE A symmetric figure is drawn on a rectangular piece of paper 28 cm by 21 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
= 28 ÷ 2
= 14 cm
Area of the large semicircle
=
12 x 3.14 x 14 x 14
= 307.72 cm
2 Breadth of the small rectangle
= 21 - 14
= 7 cm
Area of the small rectangle
= 28 x 7
= 196 cm
2 Area of the 2 smaller semicircles
= 3.14 x 7 x 7
= 153.86 cm
2 Area of the 4 boomerangs
= 196 - 153.86
= 42.14 cm
2 Area of the figure
= 42.14 + 307.72
= 349.86 cm
2 (b)
Circumference of the curved lines
= 3.14 x 28
= 87.92 cm
Perimeter of the figure
= 87.92 + 7 + 7
= 101.92 cm
Answer(s): (a) 349.86 cm
2; (b) 101.92 cm