PSLE The figure is made up of 6 identical quadrants and 2 identical semicircles. The radius of each quadrant is 10 cm. The unshaded area marked A is enclosed by 2 quadrants and 2 semicircles. (Take π = 3.14)
- Find the perimeter of F.
- Find the total shaded areas.
(a)
Perimeter of 2 semicircles
= 3.14 x 10
= 31.4 cm
Diameter of the quadrant
= 2 x 10
= 20 cm
Perimeter of 2 quadrants
=
12 x 3.14 x 20
= 31.4 cm
Perimeter of F
= 31.4 + 31.4
= 62.8 cm
(b)
Area of the large circle
= 3.14 x 10 x 10
= 314 cm
2 Area of 2 semicircles
= 3.14 x 5 x 5
= 78.5 cm
2 Area of 2 boomerangs
= Area of the rectangle - Area of the semicircle
= 20 x 10 -
12 x 3.14 x 10 x 10
= 200 - 157
= 43 cm
2 Total shaded areas
= 314 - 78.5 - 43
= 192.5 cm
2 Answer(s): (a) 62.8 cm; (b) 192.5 cm
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