PSLE A symmetric figure is drawn on a rectangular piece of paper 84 cm by 56 cm as shown. Its outline consists of a large semicircle, 3 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
= 56 - 42
= 14 cm
Area of the small rectangle
= 84 x 14
= 1176 cm
2 Area of the 3 smaller semicircles
= 1.5 x 3.14 x 14 x 14
= 923.16 cm
2 Area of the 6 boomerangs
= 1176 - 923.16
= 252.84 cm
2 Area of the figure
= 252.84 + 2769.48
= 3022.32 cm
2 (b)
Circumference of the curved lines
= 3.14 x 84
= 263.76 cm
Perimeter of the figure
= 263.76 + 14 + 14
= 291.76 cm
Answer(s): (a) 3022.32 cm
2; (b) 291.76 cm