PSLE The figure is made up of 6 identical quadrants and 2 identical semicircles. The radius of each quadrant is 35 cm. The unshaded area marked A is enclosed by 2 quadrants and 2 semicircles. (Take π = 3.14)
- Find the perimeter of F.
- Find the total shaded areas.
(a)
Perimeter of 2 semicircles
= 3.14 x 35
= 109.9 cm
Diameter of the quadrant
= 2 x 35
= 70 cm
Perimeter of 2 quadrants
=
12 x 3.14 x 70
= 109.9 cm
Perimeter of F
= 109.9 + 109.9
= 219.8 cm
(b)
Area of the large circle
= 3.14 x 35 x 35
= 3846.5 cm
2 Area of 2 semicircles
= 3.14 x 17.5 x 17.5
= 961.625 cm
2 Area of 2 boomerangs
= Area of the rectangle - Area of the semicircle
= 70 x 35 -
12 x 3.14 x 35 x 35
= 2450 - 1923.25
= 526.75 cm
2 Total shaded areas
= 3846.5 - 961.625 - 526.75
= 2358.125 cm
2 Answer(s): (a) 219.8 cm; (b) 2358.125 cm
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