PSLE The figure is made up of 6 identical quadrants and 2 identical semicircles. The radius of each quadrant is 22 cm. The unshaded area marked A is enclosed by 2 quadrants and 2 semicircles. (Take π = 3.14)
- Find the perimeter of C.
- Find the total shaded areas.
(a)
Perimeter of 2 semicircles
= 3.14 x 22
= 69.08 cm
Diameter of the quadrant
= 2 x 22
= 44 cm
Perimeter of 2 quadrants
=
12 x 3.14 x 44
= 69.08 cm
Perimeter of C
= 69.08 + 69.08
= 138.16 cm
(b)
Area of the large circle
= 3.14 x 22 x 22
= 1519.76 cm
2 Area of 2 semicircles
= 3.14 x 11 x 11
= 379.94 cm
2 Area of 2 boomerangs
= Area of the rectangle - Area of the semicircle
= 44 x 22 -
12 x 3.14 x 22 x 22
= 968 - 759.88
= 208.12 cm
2 Total shaded areas
= 1519.76 - 379.94 - 208.12
= 931.7 cm
2 Answer(s): (a) 138.16 cm; (b) 931.7 cm
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