PSLE The figure is made up of 6 identical quadrants and 2 identical semicircles. The radius of each quadrant is 44 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 44
= 138.16 cm
Diameter of the quadrant
= 2 x 44
= 88 cm
Perimeter of 2 quadrants
=
12 x 3.14 x 88
= 138.16 cm
Perimeter of S
= 138.16 + 138.16
= 276.32 cm
(b)
Area of the large circle
= 3.14 x 44 x 44
= 6079.04 cm
2 Area of 2 semicircles
= 3.14 x 22 x 22
= 1519.76 cm
2 Area of 2 boomerangs
= Area of the rectangle - Area of the semicircle
= 88 x 44 -
12 x 3.14 x 44 x 44
= 3872 - 3039.52
= 832.48 cm
2 Total shaded areas
= 6079.04 - 1519.76 - 832.48
= 3726.8 cm
2 Answer(s): (a) 276.32 cm; (b) 3726.8 cm
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