PSLE A symmetric figure is drawn on a rectangular piece of paper 72 cm by 54 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
= 72 ÷ 2
= 36 cm
Area of the large semicircle
=
12 x 3.14 x 36 x 36
= 2034.72 cm
2 Breadth of the small rectangle
= 54 - 36
= 18 cm
Area of the small rectangle
= 72 x 18
= 1296 cm
2 Area of the 2 smaller semicircles
= 3.14 x 18 x 18
= 1017.36 cm
2 Area of the 4 boomerangs
= 1296 - 1017.36
= 278.64 cm
2 Area of the figure
= 278.64 + 2034.72
= 2313.36 cm
2 (b)
Circumference of the curved lines
= 3.14 x 72
= 226.08 cm
Perimeter of the figure
= 226.08 + 18 + 18
= 262.08 cm
Answer(s): (a) 2313.36 cm
2; (b) 262.08 cm