PSLE The figure shows 6 circles, each of radius 17.5 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 17.5
= 35 cm
Perimeter of the shaded part
= Circumference of 3 circles
= 3 x
227 x 35
= 330 cm
(b)
Length of the dotted rectangle
= 4 x 17.5
= 70 cm
Breadth of the dotted rectangle
= 2 x 17.5
= 35 cm
Area of the dotted rectangle
= 70 x 35
= 2450 cm
2 Area of 2 semicircles
= Area of 1 circle
=
227 x 17.5 x 17.5
= 962.5 cm
2 Area of the shaded part
= 2450 + 962.5
= 3412.5 cm
2 Answer(s): (a) 330 cm; (b) 3412.5 cm
2