PSLE The figure is formed by two identical circles at C and E. CEDF is a square and the length of DE is 28 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 28
= 56 cm
Perimeter of the unshaded part
=
12 x 3.14 x 56
= 87.92 cm
(b)
Area of the unshaded part
= Area of the semicircle - Area of the triangle
=
12 x 3.14 x 28 x 28 -
12 x 56 x 28
= 1230.88 - 784
= 446.88 cm
2 Area of the circle
= 3.14 x 28 x 28
= 2461.76 cm
2 Total area of the shaded parts
= 2 x (Area of the circle - Area of unshaded part)
= 2 x (2461.76 - 446.88)
= 2 x 2014.88
= 4029.76 cm
2 Answer(s): (a) 87.92 cm; (b) 4029.76 cm
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