PSLE The figure is made up of 6 identical quadrants and 2 identical semicircles. The radius of each quadrant is 32 cm. The unshaded area marked A is enclosed by 2 quadrants and 2 semicircles. (Take π = 3.14)
- Find the perimeter of S.
- Find the total shaded areas.
(a)
Perimeter of 2 semicircles
= 3.14 x 32
= 100.48 cm
Diameter of the quadrant
= 2 x 32
= 64 cm
Perimeter of 2 quadrants
=
12 x 3.14 x 64
= 100.48 cm
Perimeter of S
= 100.48 + 100.48
= 200.96 cm
(b)
Area of the large circle
= 3.14 x 32 x 32
= 3215.36 cm
2 Area of 2 semicircles
= 3.14 x 16 x 16
= 803.84 cm
2 Area of 2 boomerangs
= Area of the rectangle - Area of the semicircle
= 64 x 32 -
12 x 3.14 x 32 x 32
= 2048 - 1607.68
= 440.32 cm
2 Total shaded areas
= 3215.36 - 803.84 - 440.32
= 1971.2 cm
2 Answer(s): (a) 200.96 cm; (b) 1971.2 cm
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