PSLE A symmetric figure is drawn on a rectangular piece of paper 78 cm by 52 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
= 78 ÷ 2
= 39 cm
Area of the large semicircle
=
12 x 3.14 x 39 x 39
= 2387.97 cm
2 Breadth of the small rectangle
= 52 - 39
= 13 cm
Area of the small rectangle
= 78 x 13
= 1014 cm
2 Area of the 3 smaller semicircles
= 1.5 x 3.14 x 13 x 13
= 795.99 cm
2 Area of the 6 boomerangs
= 1014 - 795.99
= 218.01 cm
2 Area of the figure
= 218.01 + 2387.97
= 2605.98 cm
2 (b)
Circumference of the curved lines
= 3.14 x 78
= 244.92 cm
Perimeter of the figure
= 244.92 + 13 + 13
= 270.92 cm
Answer(s): (a) 2605.98 cm
2; (b) 270.92 cm