PSLE A symmetric figure is drawn on a rectangular piece of paper 54 cm by 36 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
= 54 ÷ 2
= 27 cm
Area of the large semicircle
=
12 x 3.14 x 27 x 27
= 1144.53 cm
2 Breadth of the small rectangle
= 36 - 27
= 9 cm
Area of the small rectangle
= 54 x 9
= 486 cm
2 Area of the 3 smaller semicircles
= 1.5 x 3.14 x 9 x 9
= 381.51 cm
2 Area of the 6 boomerangs
= 486 - 381.51
= 104.49 cm
2 Area of the figure
= 104.49 + 1144.53
= 1249.02 cm
2 (b)
Circumference of the curved lines
= 3.14 x 54
= 169.56 cm
Perimeter of the figure
= 169.56 + 9 + 9
= 187.56 cm
Answer(s): (a) 1249.02 cm
2; (b) 187.56 cm