PSLE The figure is made up of 6 identical quadrants and 2 identical semicircles. The radius of each quadrant is 25 cm. The unshaded area marked A is enclosed by 2 quadrants and 2 semicircles. (Take π = 3.14)
- Find the perimeter of C.
- Find the total shaded areas.
(a)
Perimeter of 2 semicircles
= 3.14 x 25
= 78.5 cm
Diameter of the quadrant
= 2 x 25
= 50 cm
Perimeter of 2 quadrants
=
12 x 3.14 x 50
= 78.5 cm
Perimeter of C
= 78.5 + 78.5
= 157 cm
(b)
Area of the large circle
= 3.14 x 25 x 25
= 1962.5 cm
2 Area of 2 semicircles
= 3.14 x 12.5 x 12.5
= 490.625 cm
2 Area of 2 boomerangs
= Area of the rectangle - Area of the semicircle
= 50 x 25 -
12 x 3.14 x 25 x 25
= 1250 - 981.25
= 268.75 cm
2 Total shaded areas
= 1962.5 - 490.625 - 268.75
= 1203.125 cm
2 Answer(s): (a) 157 cm; (b) 1203.125 cm
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