The figure is not drawn to scale. It is formed by quadrants and semicircles of two sizes. The radius of the larger quadrant is 4 m longer than the radius of the smaller quadrant. The radius of the smaller quadrant (Line T) is 16 m.
- Find the area of the shaded part.
- Find the perimeter of the dotted line. (Take π = 3.14)
(a)
Radius of the big semicircle above the dotted line
= 16 + 4
= 20 m
Area of the big semicircle above the dotted line
= 3.14 x 20 x 20 x
12 = 628 m
2 Area of the small semicircle above the dotted line
= Area of the big semicircle below the dotted line
= 3.14 x 16 x 16 x
12 = 401.92 m
2 Shaded area above the dotted line
= 628 - 401.92
= 226.08 m
2 Radius of the small semicircle below the dotted line
= 16 - 4
= 12 m
Area of the small semicircle below the dotted line
= 3.14 x 12 x 12 x 16
= 226.08 m
2 Shaded area below the dotted line
= 401.92 - 226.08
= 175.84 m
2 Total shaded area
= 226.08 + 175.84
= 401.92 m
2 (b)
16 x 4 = 64 m
Circumference of the curved lines
= 3.14 x 64
= 200.96 m
Perimeter of the shaded area
= 200.96 + (4 x 2)
= 200.96 + 8
= 208.96 m
Answer(s): (a) 401.92 m
2; (b) 208.96 m