PSLE The figure is formed by two identical circles at G and J. GJHK is a square and the length of HJ is 45.5 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 45.5
= 91 cm
Perimeter of the unshaded part
=
12 x 3.14 x 91
= 142.87 cm
(b)
Area of the unshaded part
= Area of the semicircle - Area of the triangle
=
12 x 3.14 x 45.5 x 45.5 -
12 x 91 x 45.5
= 3250.2925 - 2070.25
= 1180.0425 cm
2 Area of the circle
= 3.14 x 45.5 x 45.5
= 6500.585 cm
2 Total area of the shaded parts
= 2 x (Area of the circle - Area of unshaded part)
= 2 x (6500.585 - 1180.0425)
= 2 x 5320.5425
= 10641.085 cm
2 Answer(s): (a) 142.87 cm; (b) 10641.085 cm
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