PSLE A symmetric figure is drawn on a rectangular piece of paper 138 cm by 92 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
= 138 ÷ 2
= 69 cm
Area of the large semicircle
=
12 x 3.14 x 69 x 69
= 7474.77 cm
2 Breadth of the small rectangle
= 92 - 69
= 23 cm
Area of the small rectangle
= 138 x 23
= 3174 cm
2 Area of the 3 smaller semicircles
= 1.5 x 3.14 x 23 x 23
= 2491.59 cm
2 Area of the 6 boomerangs
= 3174 - 2491.59
= 682.41 cm
2 Area of the figure
= 682.41 + 7474.77
= 8157.18 cm
2 (b)
Circumference of the curved lines
= 3.14 x 138
= 433.32 cm
Perimeter of the figure
= 433.32 + 23 + 23
= 479.32 cm
Answer(s): (a) 8157.18 cm
2; (b) 479.32 cm