PSLE The figure is made up of 6 identical quadrants and 2 identical semicircles. The radius of each quadrant is 49 cm. The unshaded area marked A is enclosed by 2 quadrants and 2 semicircles. (Take π = 3.14)
- Find the perimeter of B.
- Find the total shaded areas.
(a)
Perimeter of 2 semicircles
= 3.14 x 49
= 153.86 cm
Diameter of the quadrant
= 2 x 49
= 98 cm
Perimeter of 2 quadrants
=
12 x 3.14 x 98
= 153.86 cm
Perimeter of B
= 153.86 + 153.86
= 307.72 cm
(b)
Area of the large circle
= 3.14 x 49 x 49
= 7539.14 cm
2 Area of 2 semicircles
= 3.14 x 24.5 x 24.5
= 1884.785 cm
2 Area of 2 boomerangs
= Area of the rectangle - Area of the semicircle
= 98 x 49 -
12 x 3.14 x 49 x 49
= 4802 - 3769.57
= 1032.43 cm
2 Total shaded areas
= 7539.14 - 1884.785 - 1032.43
= 4621.925 cm
2 Answer(s): (a) 307.72 cm; (b) 4621.925 cm
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