PSLE The figure shows 4 circles, each of radius 31.5 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 31.5
= 63 cm
Perimeter of the shaded part
= Circumference of 2 circles
= 2 x
227 x 63
= 396 cm
(b)
Length of the dotted square
= Diameter of each circle
= 63 cm
Area of the dotted square
= 63 x 63
= 3969 cm
2 Area of 1 circle
=
227 x 31.5 x 31.5
= 3118.5 cm
2 Area of the shaded part
= 3969 + 3118.5
= 7087.5 cm
2 Answer(s): (a) 396 cm; (b) 7087.5 cm
2