PSLE The figure is made up of 6 identical quadrants and 3 identical semicircles. The radius of each quadrant is 9 cm. The unshaded area marked A is enclosed by 2 quadrants and 3 semicircles. (Take π = 3.14)
- Find the perimeter of V.
- Find the total shaded areas.
(a)
Diameter of the quadrant
= 2 x 9
= 18 cm
Perimeter of 2 quadrants
=
12 x 3.14 x 18
= 28.26 cm
Diameter of the semicircle
= 18 ÷ 3
= 6 cm
Perimeter of 3 semicircles
= 1
12 x 3.14 x 6
= 28.26 cm
Perimeter of V
= 28.26 + 28.26
= 56.52 cm
(b)
Area of the large circle
= 3.14 x 9 x 9
= 254.34 cm
2
Radius of 1 semicircle
= 6 ÷ 2
= 3 cm
Area of 3 semicircles
= 1
12 x 3.14 x 3 x 3
= 42.39 cm
2 Area of 2 boomerangs
= Area of the rectangle - Area of the semicircle
= 18 x 9 -
12 x 3.14 x 9 x 9
= 162 - 127.17
= 34.83 cm
2 Total shaded areas
= 254.34 - 42.39 - 34.83
= 177.12 cm
2 Answer(s): (a) 56.52 cm; (b) 177.12 cm
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