PSLE The figure is formed by two identical circles at K and M. KMLN is a square and the length of LM is 52.5 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 52.5
= 105 cm
Perimeter of the unshaded part
=
12 x 3.14 x 105
= 164.85 cm
(b)
Area of the unshaded part
= Area of the semicircle - Area of the triangle
=
12 x 3.14 x 52.5 x 52.5 -
12 x 105 x 52.5
= 4327.3125 - 2756.25
= 1571.0625 cm
2 Area of the circle
= 3.14 x 52.5 x 52.5
= 8654.625 cm
2 Total area of the shaded parts
= 2 x (Area of the circle - Area of unshaded part)
= 2 x (8654.625 - 1571.0625)
= 2 x 7083.5625
= 14167.125 cm
2 Answer(s): (a) 164.85 cm; (b) 14167.125 cm
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