PSLE The figure is made up of 6 identical quadrants and 2 identical semicircles. The radius of each quadrant is 50 cm. The unshaded area marked A is enclosed by 2 quadrants and 2 semicircles. (Take π = 3.14)
- Find the perimeter of B.
- Find the total shaded areas.
(a)
Perimeter of 2 semicircles
= 3.14 x 50
= 157 cm
Diameter of the quadrant
= 2 x 50
= 100 cm
Perimeter of 2 quadrants
=
12 x 3.14 x 100
= 157 cm
Perimeter of B
= 157 + 157
= 314 cm
(b)
Area of the large circle
= 3.14 x 50 x 50
= 7850 cm
2 Area of 2 semicircles
= 3.14 x 25 x 25
= 1962.5 cm
2 Area of 2 boomerangs
= Area of the rectangle - Area of the semicircle
= 100 x 50 -
12 x 3.14 x 50 x 50
= 5000 - 3925
= 1075 cm
2 Total shaded areas
= 7850 - 1962.5 - 1075
= 4812.5 cm
2 Answer(s): (a) 314 cm; (b) 4812.5 cm
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