PSLE The figure is formed by two identical circles at P and R. PRQS is a square and the length of QR is 10.5 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 10.5
= 21 cm
Perimeter of the unshaded part
=
12 x 3.14 x 21
= 32.97 cm
(b)
Area of the unshaded part
= Area of the semicircle - Area of the triangle
=
12 x 3.14 x 10.5 x 10.5 -
12 x 21 x 10.5
= 173.0925 - 110.25
= 62.8425 cm
2 Area of the circle
= 3.14 x 10.5 x 10.5
= 346.185 cm
2 Total area of the shaded parts
= 2 x (Area of the circle - Area of unshaded part)
= 2 x (346.185 - 62.8425)
= 2 x 283.3425
= 566.685 cm
2 Answer(s): (a) 32.97 cm; (b) 566.685 cm
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