PSLE A symmetric figure is drawn on a rectangular piece of paper 240 cm by 150 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
= 240 ÷ 2
= 120 cm
Area of the large semicircle
=
12 x 3.14 x 120 x 120
= 22608 cm
2 Breadth of the small rectangle
= 150 - 120
= 30 cm
Area of the small rectangle
= 240 x 30
= 7200 cm
2 Area of the 4 smaller semicircles
= 2 x 3.14 x 30 x 30
= 5652 cm
2 Area of the 8 boomerangs
= 7200 - 5652
= 1548 cm
2 Area of the figure
= 1548 + 22608
= 24156 cm
2 (b)
Circumference of the curved lines
= 3.14 x 240
= 753.6 cm
Perimeter of the figure
= 753.6 + 30 + 30
= 813.6 cm
Answer(s): (a) 24156 cm
2; (b) 813.6 cm