PSLE A symmetric figure is drawn on a rectangular piece of paper 60 cm by 45 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
= 60 ÷ 2
= 30 cm
Area of the large semicircle
=
12 x 3.14 x 30 x 30
= 1413 cm
2 Breadth of the small rectangle
= 45 - 30
= 15 cm
Area of the small rectangle
= 60 x 15
= 900 cm
2 Area of the 2 smaller semicircles
= 3.14 x 15 x 15
= 706.5 cm
2 Area of the 4 boomerangs
= 900 - 706.5
= 193.5 cm
2 Area of the figure
= 193.5 + 1413
= 1606.5 cm
2 (b)
Circumference of the curved lines
= 3.14 x 60
= 188.4 cm
Perimeter of the figure
= 188.4 + 15 + 15
= 218.4 cm
Answer(s): (a) 1606.5 cm
2; (b) 218.4 cm