PSLE The figure is made up of 6 identical quadrants and 2 identical semicircles. The radius of each quadrant is 29 cm. The unshaded area marked A is enclosed by 2 quadrants and 2 semicircles. (Take π = 3.14)
- Find the perimeter of D.
- Find the total shaded areas.
(a)
Perimeter of 2 semicircles
= 3.14 x 29
= 91.06 cm
Diameter of the quadrant
= 2 x 29
= 58 cm
Perimeter of 2 quadrants
=
12 x 3.14 x 58
= 91.06 cm
Perimeter of D
= 91.06 + 91.06
= 182.12 cm
(b)
Area of the large circle
= 3.14 x 29 x 29
= 2640.74 cm
2 Area of 2 semicircles
= 3.14 x 14.5 x 14.5
= 660.185 cm
2 Area of 2 boomerangs
= Area of the rectangle - Area of the semicircle
= 58 x 29 -
12 x 3.14 x 29 x 29
= 1682 - 1320.37
= 361.63 cm
2 Total shaded areas
= 2640.74 - 660.185 - 361.63
= 1618.925 cm
2 Answer(s): (a) 182.12 cm; (b) 1618.925 cm
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