PSLE The figure is made up of 6 identical quadrants and 2 identical semicircles. The radius of each quadrant is 38 cm. The unshaded area marked A is enclosed by 2 quadrants and 2 semicircles. (Take π = 3.14)
- Find the perimeter of X.
- Find the total shaded areas.
(a)
Perimeter of 2 semicircles
= 3.14 x 38
= 119.32 cm
Diameter of the quadrant
= 2 x 38
= 76 cm
Perimeter of 2 quadrants
=
12 x 3.14 x 76
= 119.32 cm
Perimeter of X
= 119.32 + 119.32
= 238.64 cm
(b)
Area of the large circle
= 3.14 x 38 x 38
= 4534.16 cm
2 Area of 2 semicircles
= 3.14 x 19 x 19
= 1133.54 cm
2 Area of 2 boomerangs
= Area of the rectangle - Area of the semicircle
= 76 x 38 -
12 x 3.14 x 38 x 38
= 2888 - 2267.08
= 620.92 cm
2 Total shaded areas
= 4534.16 - 1133.54 - 620.92
= 2779.7 cm
2 Answer(s): (a) 238.64 cm; (b) 2779.7 cm
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