PSLE The figure is made up of 6 identical quadrants and 3 identical semicircles. The radius of each quadrant is 24 cm. The unshaded area marked A is enclosed by 2 quadrants and 3 semicircles. (Take π = 3.14)
- Find the perimeter of L.
- Find the total shaded areas.
(a)
Diameter of the quadrant
= 2 x 24
= 48 cm
Perimeter of 2 quadrants
=
12 x 3.14 x 48
= 75.36 cm
Diameter of the semicircle
= 48 ÷ 3
= 16 cm
Perimeter of 3 semicircles
= 1
12 x 3.14 x 16
= 75.36 cm
Perimeter of L
= 75.36 + 75.36
= 150.72 cm
(b)
Area of the large circle
= 3.14 x 24 x 24
= 1808.64 cm
2
Radius of 1 semicircle
= 16 ÷ 2
= 8 cm
Area of 3 semicircles
= 1
12 x 3.14 x 8 x 8
= 301.44 cm
2 Area of 2 boomerangs
= Area of the rectangle - Area of the semicircle
= 48 x 24 -
12 x 3.14 x 24 x 24
= 1152 - 904.32
= 247.68 cm
2 Total shaded areas
= 1808.64 - 301.44 - 247.68
= 1259.52 cm
2 Answer(s): (a) 150.72 cm; (b) 1259.52 cm
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