PSLE The figure is made up of 6 identical quadrants and 2 identical semicircles. The radius of each quadrant is 21 cm. The unshaded area marked A is enclosed by 2 quadrants and 2 semicircles. (Take π = 3.14)
- Find the perimeter of V.
- Find the total shaded areas.
(a)
Perimeter of 2 semicircles
= 3.14 x 21
= 65.94 cm
Diameter of the quadrant
= 2 x 21
= 42 cm
Perimeter of 2 quadrants
=
12 x 3.14 x 42
= 65.94 cm
Perimeter of V
= 65.94 + 65.94
= 131.88 cm
(b)
Area of the large circle
= 3.14 x 21 x 21
= 1384.74 cm
2 Area of 2 semicircles
= 3.14 x 10.5 x 10.5
= 346.185 cm
2 Area of 2 boomerangs
= Area of the rectangle - Area of the semicircle
= 42 x 21 -
12 x 3.14 x 21 x 21
= 882 - 692.37
= 189.63 cm
2 Total shaded areas
= 1384.74 - 346.185 - 189.63
= 848.925 cm
2 Answer(s): (a) 131.88 cm; (b) 848.925 cm
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