PSLE A symmetric figure is drawn on a rectangular piece of paper 90 cm by 60 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
= 90 ÷ 2
= 45 cm
Area of the large semicircle
=
12 x 3.14 x 45 x 45
= 3179.25 cm
2 Breadth of the small rectangle
= 60 - 45
= 15 cm
Area of the small rectangle
= 90 x 15
= 1350 cm
2 Area of the 3 smaller semicircles
= 1.5 x 3.14 x 15 x 15
= 1059.75 cm
2 Area of the 6 boomerangs
= 1350 - 1059.75
= 290.25 cm
2 Area of the figure
= 290.25 + 3179.25
= 3469.5 cm
2 (b)
Circumference of the curved lines
= 3.14 x 90
= 282.6 cm
Perimeter of the figure
= 282.6 + 15 + 15
= 312.6 cm
Answer(s): (a) 3469.5 cm
2; (b) 312.6 cm