PSLE The figure is formed by two identical circles at D and F. DFEG is a square and the length of EF is 49 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 49
= 98 cm
Perimeter of the unshaded part
=
12 x 3.14 x 98
= 153.86 cm
(b)
Area of the unshaded part
= Area of the semicircle - Area of the triangle
=
12 x 3.14 x 49 x 49 -
12 x 98 x 49
= 3769.57 - 2401
= 1368.57 cm
2 Area of the circle
= 3.14 x 49 x 49
= 7539.14 cm
2 Total area of the shaded parts
= 2 x (Area of the circle - Area of unshaded part)
= 2 x (7539.14 - 1368.57)
= 2 x 6170.57
= 12341.14 cm
2 Answer(s): (a) 153.86 cm; (b) 12341.14 cm
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