PSLE The figure shows 6 circles, each of radius 3.5 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 3.5
= 7 cm
Perimeter of the shaded part
= Circumference of 3 circles
= 3 x
227 x 7
= 66 cm
(b)
Length of the dotted rectangle
= 6 x 3.5
= 21 cm
Breath of the dotted rectangle
= 2 x 3.5
= 7 cm
Area of the dotted rectangle
= 21 x 7
= 147 cm
2 Area of 2 semicircles
= Area of 1 circle
=
227 x 3.5 x 3.5
= 38.5 cm
2 Area of the shaded part
= 147 + 38.5
= 185.5 cm
2 Answer(s): (a) 66 cm; (b) 185.5 cm
2