PSLE The figure is made up of 6 identical quadrants and 2 identical semicircles. The radius of each quadrant is 46 cm. The unshaded area marked A is enclosed by 2 quadrants and 2 semicircles. (Take π = 3.14)
- Find the perimeter of W.
- Find the total shaded areas.
(a)
Perimeter of 2 semicircles
= 3.14 x 46
= 144.44 cm
Diameter of the quadrant
= 2 x 46
= 92 cm
Perimeter of 2 quadrants
=
12 x 3.14 x 92
= 144.44 cm
Perimeter of W
= 144.44 + 144.44
= 288.88 cm
(b)
Area of the large circle
= 3.14 x 46 x 46
= 6644.24 cm
2 Area of 2 semicircles
= 3.14 x 23 x 23
= 1661.06 cm
2 Area of 2 boomerangs
= Area of the rectangle - Area of the semicircle
= 92 x 46 -
12 x 3.14 x 46 x 46
= 4232 - 3322.12
= 909.88 cm
2 Total shaded areas
= 6644.24 - 1661.06 - 909.88
= 4073.3 cm
2 Answer(s): (a) 288.88 cm; (b) 4073.3 cm
2