PSLE A symmetric figure is drawn on a rectangular piece of paper 84 cm by 63 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
= 84 ÷ 2
= 42 cm
Area of the large semicircle
=
12 x 3.14 x 42 x 42
= 2769.48 cm
2 Breadth of the small rectangle
= 63 - 42
= 21 cm
Area of the small rectangle
= 84 x 21
= 1764 cm
2 Area of the 2 smaller semicircles
= 3.14 x 21 x 21
= 1384.74 cm
2 Area of the 4 boomerangs
= 1764 - 1384.74
= 379.26 cm
2 Area of the figure
= 379.26 + 2769.48
= 3148.74 cm
2 (b)
Circumference of the curved lines
= 3.14 x 84
= 263.76 cm
Perimeter of the figure
= 263.76 + 21 + 21
= 305.76 cm
Answer(s): (a) 3148.74 cm
2; (b) 305.76 cm