PSLE The figure is made up of 6 identical quadrants and 2 identical semicircles. The radius of each quadrant is 19 cm. The unshaded area marked A is enclosed by 2 quadrants and 2 semicircles. (Take π = 3.14)
- Find the perimeter of S.
- Find the total shaded areas.
(a)
Perimeter of 2 semicircles
= 3.14 x 19
= 59.66 cm
Diameter of the quadrant
= 2 x 19
= 38 cm
Perimeter of 2 quadrants
=
12 x 3.14 x 38
= 59.66 cm
Perimeter of S
= 59.66 + 59.66
= 119.32 cm
(b)
Area of the large circle
= 3.14 x 19 x 19
= 1133.54 cm
2 Area of 2 semicircles
= 3.14 x 9.5 x 9.5
= 283.385 cm
2 Area of 2 boomerangs
= Area of the rectangle - Area of the semicircle
= 38 x 19 -
12 x 3.14 x 19 x 19
= 722 - 566.77
= 155.23 cm
2 Total shaded areas
= 1133.54 - 283.385 - 155.23
= 694.925 cm
2 Answer(s): (a) 119.32 cm; (b) 694.925 cm
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