PSLE The figure is formed by two identical circles at N and Q. NQPR is a square and the length of PQ is 31.5 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 31.5
= 63 cm
Perimeter of the unshaded part
=
12 x 3.14 x 63
= 98.91 cm
(b)
Area of the unshaded part
= Area of the semicircle - Area of the triangle
=
12 x 3.14 x 31.5 x 31.5 -
12 x 63 x 31.5
= 1557.8325 - 992.25
= 565.5825 cm
2 Area of the circle
= 3.14 x 31.5 x 31.5
= 3115.665 cm
2 Total area of the shaded parts
= 2 x (Area of the circle - Area of unshaded part)
= 2 x (3115.665 - 565.5825)
= 2 x 2550.0825
= 5100.165 cm
2 Answer(s): (a) 98.91 cm; (b) 5100.165 cm
2