PSLE A symmetric figure is drawn on a rectangular piece of paper 112 cm by 70 cm as shown. Its outline consists of a large semicircle, 4 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
= 112 ÷ 2
= 56 cm
Area of the large semicircle
=
12 x 3.14 x 56 x 56
= 4923.52 cm
2 Breadth of the small rectangle
= 70 - 56
= 14 cm
Area of the small rectangle
= 112 x 14
= 1568 cm
2 Area of the 4 smaller semicircles
= 2 x 3.14 x 14 x 14
= 1230.88 cm
2 Area of the 8 boomerangs
= 1568 - 1230.88
= 337.12 cm
2 Area of the figure
= 337.12 + 4923.52
= 5260.64 cm
2 (b)
Circumference of the curved lines
= 3.14 x 112
= 351.68 cm
Perimeter of the figure
= 351.68 + 14 + 14
= 379.68 cm
Answer(s): (a) 5260.64 cm
2; (b) 379.68 cm