PSLE The figure is made up of 6 identical quadrants and 3 identical semicircles. The radius of each quadrant is 33 cm. The unshaded area marked A is enclosed by 2 quadrants and 3 semicircles. (Take π = 3.14)
- Find the perimeter of T.
- Find the total shaded areas.
(a)
Diameter of the quadrant
= 2 x 33
= 66 cm
Perimeter of 2 quadrants
=
12 x 3.14 x 66
= 103.62 cm
Diameter of the semicircle
= 66 ÷ 3
= 22 cm
Perimeter of 3 semicircles
= 1
12 x 3.14 x 22
= 103.62 cm
Perimeter of T
= 103.62 + 103.62
= 207.24 cm
(b)
Area of the large circle
= 3.14 x 33 x 33
= 3419.46 cm
2
Radius of 1 semicircle
= 22 ÷ 2
= 11 cm
Area of 3 semicircles
= 1
12 x 3.14 x 11 x 11
= 569.91 cm
2 Area of 2 boomerangs
= Area of the rectangle - Area of the semicircle
= 66 x 33 -
12 x 3.14 x 33 x 33
= 2178 - 1709.73
= 468.27 cm
2 Total shaded areas
= 3419.46 - 569.91 - 468.27
= 2381.28 cm
2 Answer(s): (a) 207.24 cm; (b) 2381.28 cm
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