PSLE A symmetric figure is drawn on a rectangular piece of paper 60 cm by 40 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
= 60 ÷ 2
= 30 cm
Area of the large semicircle
=
12 x 3.14 x 30 x 30
= 1413 cm
2 Breadth of the small rectangle
= 40 - 30
= 10 cm
Area of the small rectangle
= 60 x 10
= 600 cm
2 Area of the 3 smaller semicircles
= 1.5 x 3.14 x 10 x 10
= 471 cm
2 Area of the 6 boomerangs
= 600 - 471
= 129 cm
2 Area of the figure
= 129 + 1413
= 1542 cm
2 (b)
Circumference of the curved lines
= 3.14 x 60
= 188.4 cm
Perimeter of the figure
= 188.4 + 10 + 10
= 208.4 cm
Answer(s): (a) 1542 cm
2; (b) 208.4 cm