The figure is made up of a circle, a rectangle and 2 semicircles. CE, the diameter of the circle, is 60 m, CD is 48 m and DE is 36 m.
- What is the total area of the shaded parts?
- What is the total perimeter of the shaded parts? (Take π = 3.14)
(a)
Radius of CD
= 48 ÷ 2
= 24 m
Area of Semicircle CD
=
12 x 24 x 24 x 3.14
= 904.32 m
2
Radius of DE
= 36 ÷ 2
= 18 m
Area of Semicircle DE
=
12 x 18 x 18 x 3.14
= 508.68 m
2 Radius of CE
= 60 ÷ 2
= 30 m
Area of the semicircle CE = Radius CE
=
12 x 30 x 30 x 3.14
= 1413 m
2 Total area of shaded parts
= 904.32 + 508.68 +
12 x 48 x 36 - 1413
= 864 m
2 (b)
Length of Semicircle CD
=
12 x 3.14 x 48
= 75.36 m
Length of Semicircle DE
=
12 x 3.14 x 36
= 56.52 m
Length of Semicircle CE
=
12 x 3.14 x 60
= 94.2 m
Perimeter of shaded parts
= 75.36 + 56.52 + 94.2
= 904.32 m
Answer(s): (a) 864 m
2; (b) 904.32 m