PSLE A symmetric figure is drawn on a rectangular piece of paper 42 cm by 28 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
= 42 ÷ 2
= 21 cm
Area of the large semicircle
=
12 x 3.14 x 21 x 21
= 692.37 cm
2 Breadth of the small rectangle
= 28 - 21
= 7 cm
Area of the small rectangle
= 42 x 7
= 294 cm
2 Area of the 3 smaller semicircles
= 1.5 x 3.14 x 7 x 7
= 230.79 cm
2 Area of the 6 boomerangs
= 294 - 230.79
= 63.21 cm
2 Area of the figure
= 63.21 + 692.37
= 755.58 cm
2 (b)
Circumference of the curved lines
= 3.14 x 42
= 131.88 cm
Perimeter of the figure
= 131.88 + 7 + 7
= 145.88 cm
Answer(s): (a) 755.58 cm
2; (b) 145.88 cm