PSLE A symmetric figure is drawn on a rectangular piece of paper 128 cm by 80 cm as shown. Its outline consists of a large semicircle, 4 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
= 128 ÷ 2
= 64 cm
Area of the large semicircle
=
12 x 3.14 x 64 x 64
= 6430.72 cm
2 Breadth of the small rectangle
= 80 - 64
= 16 cm
Area of the small rectangle
= 128 x 16
= 2048 cm
2 Area of the 4 smaller semicircles
= 2 x 3.14 x 16 x 16
= 1607.68 cm
2 Area of the 8 boomerangs
= 2048 - 1607.68
= 440.32 cm
2 Area of the figure
= 440.32 + 6430.72
= 6871.04 cm
2 (b)
Circumference of the curved lines
= 3.14 x 128
= 401.92 cm
Perimeter of the figure
= 401.92 + 16 + 16
= 433.92 cm
Answer(s): (a) 6871.04 cm
2; (b) 433.92 cm