PSLE The figure is formed by two identical circles at J and L. JLKM is a square and the length of KL is 21 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 21
= 42 cm
Perimeter of the unshaded part
=
12 x 3.14 x 42
= 65.94 cm
(b)
Area of the unshaded part
= Area of the semicircle - Area of the triangle
=
12 x 3.14 x 21 x 21 -
12 x 42 x 21
= 692.37 - 441
= 251.37 cm
2 Area of the circle
= 3.14 x 21 x 21
= 1384.74 cm
2 Total area of the shaded parts
= 2 x (Area of the circle - Area of unshaded part)
= 2 x (1384.74 - 251.37)
= 2 x 1133.37
= 2266.74 cm
2 Answer(s): (a) 65.94 cm; (b) 2266.74 cm
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