PSLE The figure is made up of 6 identical quadrants and 2 identical semicircles. The radius of each quadrant is 28 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 28
= 87.92 cm
Diameter of the quadrant
= 2 x 28
= 56 cm
Perimeter of 2 quadrants
=
12 x 3.14 x 56
= 87.92 cm
Perimeter of S
= 87.92 + 87.92
= 175.84 cm
(b)
Area of the large circle
= 3.14 x 28 x 28
= 2461.76 cm
2 Area of 2 semicircles
= 3.14 x 14 x 14
= 615.44 cm
2 Area of 2 boomerangs
= Area of the rectangle - Area of the semicircle
= 56 x 28 -
12 x 3.14 x 28 x 28
= 1568 - 1230.88
= 337.12 cm
2 Total shaded areas
= 2461.76 - 615.44 - 337.12
= 1509.2 cm
2 Answer(s): (a) 175.84 cm; (b) 1509.2 cm
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