PSLE The figure is made up of 6 identical quadrants and 2 identical semicircles. The radius of each quadrant is 34 cm. The unshaded area marked A is enclosed by 2 quadrants and 2 semicircles. (Take π = 3.14)
- Find the perimeter of N.
- Find the total shaded areas.
(a)
Perimeter of 2 semicircles
= 3.14 x 34
= 106.76 cm
Diameter of the quadrant
= 2 x 34
= 68 cm
Perimeter of 2 quadrants
=
12 x 3.14 x 68
= 106.76 cm
Perimeter of N
= 106.76 + 106.76
= 213.52 cm
(b)
Area of the large circle
= 3.14 x 34 x 34
= 3629.84 cm
2 Area of 2 semicircles
= 3.14 x 17 x 17
= 907.46 cm
2 Area of 2 boomerangs
= Area of the rectangle - Area of the semicircle
= 68 x 34 -
12 x 3.14 x 34 x 34
= 2312 - 1814.92
= 497.08 cm
2 Total shaded areas
= 3629.84 - 907.46 - 497.08
= 2225.3 cm
2 Answer(s): (a) 213.52 cm; (b) 2225.3 cm
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