PSLE The figure is made up of 6 identical quadrants and 2 identical semicircles. The radius of each quadrant is 23 cm. The unshaded area marked A is enclosed by 2 quadrants and 2 semicircles. (Take π = 3.14)
- Find the perimeter of R.
- Find the total shaded areas.
(a)
Perimeter of 2 semicircles
= 3.14 x 23
= 72.22 cm
Diameter of the quadrant
= 2 x 23
= 46 cm
Perimeter of 2 quadrants
=
12 x 3.14 x 46
= 72.22 cm
Perimeter of R
= 72.22 + 72.22
= 144.44 cm
(b)
Area of the large circle
= 3.14 x 23 x 23
= 1661.06 cm
2 Area of 2 semicircles
= 3.14 x 11.5 x 11.5
= 415.265 cm
2 Area of 2 boomerangs
= Area of the rectangle - Area of the semicircle
= 46 x 23 -
12 x 3.14 x 23 x 23
= 1058 - 830.53
= 227.47 cm
2 Total shaded areas
= 1661.06 - 415.265 - 227.47
= 1018.325 cm
2 Answer(s): (a) 144.44 cm; (b) 1018.325 cm
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