PSLE The figure is made up of 6 identical quadrants and 2 identical semicircles. The radius of each quadrant is 27 cm. The unshaded area marked A is enclosed by 2 quadrants and 2 semicircles. (Take π = 3.14)
- Find the perimeter of A.
- Find the total shaded areas.
(a)
Perimeter of 2 semicircles
= 3.14 x 27
= 84.78 cm
Diameter of the quadrant
= 2 x 27
= 54 cm
Perimeter of 2 quadrants
=
12 x 3.14 x 54
= 84.78 cm
Perimeter of A
= 84.78 + 84.78
= 169.56 cm
(b)
Area of the large circle
= 3.14 x 27 x 27
= 2289.06 cm
2 Area of 2 semicircles
= 3.14 x 13.5 x 13.5
= 572.265 cm
2 Area of 2 boomerangs
= Area of the rectangle - Area of the semicircle
= 54 x 27 -
12 x 3.14 x 27 x 27
= 1458 - 1144.53
= 313.47 cm
2 Total shaded areas
= 2289.06 - 572.265 - 313.47
= 1403.325 cm
2 Answer(s): (a) 169.56 cm; (b) 1403.325 cm
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