PSLE The figure is made up of 6 identical quadrants and 2 identical semicircles. The radius of each quadrant is 13 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 13
= 40.82 cm
Diameter of the quadrant
= 2 x 13
= 26 cm
Perimeter of 2 quadrants
=
12 x 3.14 x 26
= 40.82 cm
Perimeter of N
= 40.82 + 40.82
= 81.64 cm
(b)
Area of the large circle
= 3.14 x 13 x 13
= 530.66 cm
2 Area of 2 semicircles
= 3.14 x 6.5 x 6.5
= 132.665 cm
2 Area of 2 boomerangs
= Area of the rectangle - Area of the semicircle
= 26 x 13 -
12 x 3.14 x 13 x 13
= 338 - 265.33
= 72.67 cm
2 Total shaded areas
= 530.66 - 132.665 - 72.67
= 325.325 cm
2 Answer(s): (a) 81.64 cm; (b) 325.325 cm
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