PSLE A symmetric figure is drawn on a rectangular piece of paper 150 cm by 100 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
= 150 ÷ 2
= 75 cm
Area of the large semicircle
=
12 x 3.14 x 75 x 75
= 8831.25 cm
2 Breadth of the small rectangle
= 100 - 75
= 25 cm
Area of the small rectangle
= 150 x 25
= 3750 cm
2 Area of the 3 smaller semicircles
= 1.5 x 3.14 x 25 x 25
= 2943.75 cm
2 Area of the 6 boomerangs
= 3750 - 2943.75
= 806.25 cm
2 Area of the figure
= 806.25 + 8831.25
= 9637.5 cm
2 (b)
Circumference of the curved lines
= 3.14 x 150
= 471 cm
Perimeter of the figure
= 471 + 25 + 25
= 521 cm
Answer(s): (a) 9637.5 cm
2; (b) 521 cm