PSLE The figure is made up of 6 identical quadrants and 2 identical semicircles. The radius of each quadrant is 26 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 26
= 81.64 cm
Diameter of the quadrant
= 2 x 26
= 52 cm
Perimeter of 2 quadrants
=
12 x 3.14 x 52
= 81.64 cm
Perimeter of X
= 81.64 + 81.64
= 163.28 cm
(b)
Area of the large circle
= 3.14 x 26 x 26
= 2122.64 cm
2 Area of 2 semicircles
= 3.14 x 13 x 13
= 530.66 cm
2 Area of 2 boomerangs
= Area of the rectangle - Area of the semicircle
= 52 x 26 -
12 x 3.14 x 26 x 26
= 1352 - 1061.32
= 290.68 cm
2 Total shaded areas
= 2122.64 - 530.66 - 290.68
= 1301.3 cm
2 Answer(s): (a) 163.28 cm; (b) 1301.3 cm
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