PSLE The figure is formed by two identical circles at N and Q. NQPR is a square and the length of PQ is 35 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 35
= 70 cm
Perimeter of the unshaded part
=
12 x 3.14 x 70
= 109.9 cm
(b)
Area of the unshaded part
= Area of the semicircle - Area of the triangle
=
12 x 3.14 x 35 x 35 -
12 x 70 x 35
= 1923.25 - 1225
= 698.25 cm
2 Area of the circle
= 3.14 x 35 x 35
= 3846.5 cm
2 Total area of the shaded parts
= 2 x (Area of the circle - Area of unshaded part)
= 2 x (3846.5 - 698.25)
= 2 x 3148.25
= 6296.5 cm
2 Answer(s): (a) 109.9 cm; (b) 6296.5 cm
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