The figure is not drawn to scale. It is formed by quadrants and semicircles of two sizes. The radius of the larger quadrant is 7 m longer than the radius of the smaller quadrant. The radius of the smaller quadrant (Line M) is 32 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
= 32 + 7
= 39 m
Area of the big semicircle above the dotted line
= 3.14 x 39 x 39 x
12 = 2387.97 m
2 Area of the small semicircle above the dotted line
= Area of the big semicircle below the dotted line
= 3.14 x 32 x 32 x
12 = 1607.68 m
2 Shaded area above the dotted line
= 2387.97 - 1607.68
= 780.29 m
2 Radius of the small semicircle below the dotted line
= 32 - 7
= 25 m
Area of the small semicircle below the dotted line
= 3.14 x 25 x 25 x 32
= 780.29 m
2 Shaded area below the dotted line
= 1607.68 - 780.29
= 827.39 m
2 Total shaded area
= 780.29 + 827.39
= 1607.68 m
2 (b)
32 x 4 = 128 m
Circumference of the curved lines
= 3.14 x 128
= 401.92 m
Perimeter of the shaded area
= 401.92 + (7 x 2)
= 401.92 + 14
= 415.92 m
Answer(s): (a) 1607.68 m
2; (b) 415.92 m