PSLE The figure is made up of 6 identical quadrants and 2 identical semicircles. The radius of each quadrant is 37 cm. The unshaded area marked A is enclosed by 2 quadrants and 2 semicircles. (Take π = 3.14)
- Find the perimeter of D.
- Find the total shaded areas.
(a)
Perimeter of 2 semicircles
= 3.14 x 37
= 116.18 cm
Diameter of the quadrant
= 2 x 37
= 74 cm
Perimeter of 2 quadrants
=
12 x 3.14 x 74
= 116.18 cm
Perimeter of D
= 116.18 + 116.18
= 232.36 cm
(b)
Area of the large circle
= 3.14 x 37 x 37
= 4298.66 cm
2 Area of 2 semicircles
= 3.14 x 18.5 x 18.5
= 1074.665 cm
2 Area of 2 boomerangs
= Area of the rectangle - Area of the semicircle
= 74 x 37 -
12 x 3.14 x 37 x 37
= 2738 - 2149.33
= 588.67 cm
2 Total shaded areas
= 4298.66 - 1074.665 - 588.67
= 2635.325 cm
2 Answer(s): (a) 232.36 cm; (b) 2635.325 cm
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