PSLE The figure is formed by two identical circles at E and G. EGFH is a square and the length of FG is 70 cm. (Take π = 3.14)
- Find the perimeter of the unshaded part.
- Find the total area of the shaded parts.
(a)
Diameter of the circle
= 2 x 70
= 140 cm
Perimeter of the unshaded part
=
12 x 3.14 x 140
= 219.8 cm
(b)
Area of the unshaded part
= Area of the semicircle - Area of the triangle
=
12 x 3.14 x 70 x 70 -
12 x 140 x 70
= 7693 - 4900
= 2793 cm
2 Area of the circle
= 3.14 x 70 x 70
= 15386 cm
2 Total area of the shaded parts
= 2 x (Area of the circle - Area of unshaded part)
= 2 x (15386 - 2793)
= 2 x 12593
= 25186 cm
2 Answer(s): (a) 219.8 cm; (b) 25186 cm
2