PSLE The figure is formed by two identical circles at H and K. HKJL is a square and the length of JK is 42 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 42
= 84 cm
Perimeter of the unshaded part
=
12 x 3.14 x 84
= 131.88 cm
(b)
Area of the unshaded part
= Area of the semicircle - Area of the triangle
=
12 x 3.14 x 42 x 42 -
12 x 84 x 42
= 2769.48 - 1764
= 1005.48 cm
2 Area of the circle
= 3.14 x 42 x 42
= 5538.96 cm
2 Total area of the shaded parts
= 2 x (Area of the circle - Area of unshaded part)
= 2 x (5538.96 - 1005.48)
= 2 x 4533.48
= 9066.96 cm
2 Answer(s): (a) 131.88 cm; (b) 9066.96 cm
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