PSLE The figure is made up of 6 identical quadrants and 2 identical semicircles. The radius of each quadrant is 40 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 40
= 125.6 cm
Diameter of the quadrant
= 2 x 40
= 80 cm
Perimeter of 2 quadrants
=
12 x 3.14 x 80
= 125.6 cm
Perimeter of R
= 125.6 + 125.6
= 251.2 cm
(b)
Area of the large circle
= 3.14 x 40 x 40
= 5024 cm
2 Area of 2 semicircles
= 3.14 x 20 x 20
= 1256 cm
2 Area of 2 boomerangs
= Area of the rectangle - Area of the semicircle
= 80 x 40 -
12 x 3.14 x 40 x 40
= 3200 - 2512
= 688 cm
2 Total shaded areas
= 5024 - 1256 - 688
= 3080 cm
2 Answer(s): (a) 251.2 cm; (b) 3080 cm
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