PSLE The figure shows 6 circles, each of radius 42 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 42
= 84 cm
Perimeter of the shaded part
= Circumference of 3 circles
= 3 x
227 x 84
= 792 cm
(b)
Length of the dotted rectangle
= 6 x 42
= 252 cm
Breath of the dotted rectangle
= 2 x 42
= 84 cm
Area of the dotted rectangle
= 252 x 84
= 21168 cm
2 Area of 2 semicircles
= Area of 1 circle
=
227 x 42 x 42
= 5544 cm
2 Area of the shaded part
= 21168 + 5544
= 26712 cm
2 Answer(s): (a) 792 cm; (b) 26712 cm
2