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 cm longer than the radius of the smaller quadrant. The radius of the smaller quadrant (Line M) is 22 cm.
- 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
= 22 + 7
= 29 cm
Area of the big semicircle above the dotted line
= 3.14 x 29 x 29 x
12 = 1320.37 cm
2 Area of the small semicircle above the dotted line
= Area of the big semicircle below the dotted line
= 3.14 x 22 x 22 x
12 = 759.88 cm
2 Shaded area above the dotted line
= 1320.37 - 759.88
= 560.49 cm
2 Radius of the small semicircle below the dotted line
= 22 - 7
= 15 cm
Area of the small semicircle below the dotted line
= 3.14 x 15 x 15 x 22
= 560.49 cm
2 Shaded area below the dotted line
= 759.88 - 560.49
= 199.39 cm
2 Total shaded area
= 560.49 + 199.39
= 759.88 cm
2 (b)
22 x 4 = 88 cm
Circumference of the curved lines
= 3.14 x 88
= 276.32 cm
Perimeter of the shaded area
= 276.32 + (7 x 2)
= 276.32 + 14
= 290.32 cm
Answer(s): (a) 759.88 cm
2; (b) 290.32 cm