PSLE A symmetric figure is drawn on a rectangular piece of paper 120 cm by 75 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
= 120 ÷ 2
= 60 cm
Area of the large semicircle
=
12 x 3.14 x 60 x 60
= 5652 cm
2 Breadth of the small rectangle
= 75 - 60
= 15 cm
Area of the small rectangle
= 120 x 15
= 1800 cm
2 Area of the 4 smaller semicircles
= 2 x 3.14 x 15 x 15
= 1413 cm
2 Area of the 8 boomerangs
= 1800 - 1413
= 387 cm
2 Area of the figure
= 387 + 5652
= 6039 cm
2 (b)
Circumference of the curved lines
= 3.14 x 120
= 376.8 cm
Perimeter of the figure
= 376.8 + 15 + 15
= 406.8 cm
Answer(s): (a) 6039 cm
2; (b) 406.8 cm