PSLE The figure is formed by two identical circles at N and Q. NQPR is a square and the length of PQ is 66.5 cm. (Take π = 3.14)
- Find the perimeter of the unshaded part.
- Find the total area of the shaded parts.
(a)
Diameter of the circle
= 2 x 66.5
= 133 cm
Perimeter of the unshaded part
=
12 x 3.14 x 133
= 208.81 cm
(b)
Area of the unshaded part
= Area of the semicircle - Area of the triangle
=
12 x 3.14 x 66.5 x 66.5 -
12 x 133 x 66.5
= 6942.9325 - 4422.25
= 2520.6825 cm
2 Area of the circle
= 3.14 x 66.5 x 66.5
= 13885.865 cm
2 Total area of the shaded parts
= 2 x (Area of the circle - Area of unshaded part)
= 2 x (13885.865 - 2520.6825)
= 2 x 11365.1825
= 22730.365 cm
2 Answer(s): (a) 208.81 cm; (b) 22730.365 cm
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