PSLE The figure shows 6 circles, each of radius 10.5 cm. Each circle touches the circles next to it.
(Take π =
227)
- Find the perimeter of the shaded part.
- Find the area of the shaded part.
(a)
Diameter of each circle
= 2 x 10.5
= 21 cm
Perimeter of the shaded part
= Circumference of 3 circles
= 3 x
227 x 21
= 198 cm
(b)
Length of the dotted rectangle
= 4 x 10.5
= 42 cm
Breadth of the dotted rectangle
= 2 x 10.5
= 21 cm
Area of the dotted rectangle
= 42 x 21
= 882 cm
2 Area of 2 semicircles
= Area of 1 circle
=
227 x 10.5 x 10.5
= 346.5 cm
2 Area of the shaded part
= 882 + 346.5
= 1228.5 cm
2 Answer(s): (a) 198 cm; (b) 1228.5 cm
2