PSLE The figure is made up of 6 identical quadrants and 2 identical semicircles. The radius of each quadrant is 41 cm. The unshaded area marked A is enclosed by 2 quadrants and 2 semicircles. (Take π = 3.14)
- Find the perimeter of M.
- Find the total shaded areas.
(a)
Perimeter of 2 semicircles
= 3.14 x 41
= 128.74 cm
Diameter of the quadrant
= 2 x 41
= 82 cm
Perimeter of 2 quadrants
=
12 x 3.14 x 82
= 128.74 cm
Perimeter of M
= 128.74 + 128.74
= 257.48 cm
(b)
Area of the large circle
= 3.14 x 41 x 41
= 5278.34 cm
2 Area of 2 semicircles
= 3.14 x 20.5 x 20.5
= 1319.585 cm
2 Area of 2 boomerangs
= Area of the rectangle - Area of the semicircle
= 82 x 41 -
12 x 3.14 x 41 x 41
= 3362 - 2639.17
= 722.83 cm
2 Total shaded areas
= 5278.34 - 1319.585 - 722.83
= 3235.925 cm
2 Answer(s): (a) 257.48 cm; (b) 3235.925 cm
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