PSLE A symmetric figure is drawn on a rectangular piece of paper 100 cm by 75 cm as shown. Its outline consists of a large semicircle, 2 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
= 100 ÷ 2
= 50 cm
Area of the large semicircle
=
12 x 3.14 x 50 x 50
= 3925 cm
2 Breadth of the small rectangle
= 75 - 50
= 25 cm
Area of the small rectangle
= 100 x 25
= 2500 cm
2 Area of the 2 smaller semicircles
= 3.14 x 25 x 25
= 1962.5 cm
2 Area of the 4 boomerangs
= 2500 - 1962.5
= 537.5 cm
2 Area of the figure
= 537.5 + 3925
= 4462.5 cm
2 (b)
Circumference of the curved lines
= 3.14 x 100
= 314 cm
Perimeter of the figure
= 314 + 25 + 25
= 364 cm
Answer(s): (a) 4462.5 cm
2; (b) 364 cm