PSLE The figure is made up of 6 identical quadrants and 3 identical semicircles. The radius of each quadrant is 6 cm. The unshaded area marked A is enclosed by 2 quadrants and 3 semicircles. (Take π = 3.14)
- Find the perimeter of G.
- Find the total shaded areas.
(a)
Diameter of the quadrant
= 2 x 6
= 12 cm
Perimeter of 2 quadrants
=
12 x 3.14 x 12
= 18.84 cm
Diameter of the semicircle
= 12 ÷ 3
= 4 cm
Perimeter of 3 semicircles
= 1
12 x 3.14 x 4
= 18.84 cm
Perimeter of G
= 18.84 + 18.84
= 37.68 cm
(b)
Area of the large circle
= 3.14 x 6 x 6
= 113.04 cm
2
Radius of 1 semicircle
= 4 ÷ 2
= 2 cm
Area of 3 semicircles
= 1
12 x 3.14 x 2 x 2
= 18.84 cm
2 Area of 2 boomerangs
= Area of the rectangle - Area of the semicircle
= 12 x 6 -
12 x 3.14 x 6 x 6
= 72 - 56.52
= 15.48 cm
2 Total shaded areas
= 113.04 - 18.84 - 15.48
= 78.72 cm
2 Answer(s): (a) 37.68 cm; (b) 78.72 cm
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