PSLE The figure is made up of 6 identical quadrants and 2 identical semicircles. The radius of each quadrant is 47 cm. The unshaded area marked A is enclosed by 2 quadrants and 2 semicircles. (Take π = 3.14)
- Find the perimeter of T.
- Find the total shaded areas.
(a)
Perimeter of 2 semicircles
= 3.14 x 47
= 147.58 cm
Diameter of the quadrant
= 2 x 47
= 94 cm
Perimeter of 2 quadrants
=
12 x 3.14 x 94
= 147.58 cm
Perimeter of T
= 147.58 + 147.58
= 295.16 cm
(b)
Area of the large circle
= 3.14 x 47 x 47
= 6936.26 cm
2 Area of 2 semicircles
= 3.14 x 23.5 x 23.5
= 1734.065 cm
2 Area of 2 boomerangs
= Area of the rectangle - Area of the semicircle
= 94 x 47 -
12 x 3.14 x 47 x 47
= 4418 - 3468.13
= 949.87 cm
2 Total shaded areas
= 6936.26 - 1734.065 - 949.87
= 4252.325 cm
2 Answer(s): (a) 295.16 cm; (b) 4252.325 cm
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