PSLE The figure is formed by two identical circles at Q and S. QSRT is a square and the length of RS is 38.5 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 38.5
= 77 cm
Perimeter of the unshaded part
=
12 x 3.14 x 77
= 120.89 cm
(b)
Area of the unshaded part
= Area of the semicircle - Area of the triangle
=
12 x 3.14 x 38.5 x 38.5 -
12 x 77 x 38.5
= 2327.1325 - 1482.25
= 844.8825 cm
2 Area of the circle
= 3.14 x 38.5 x 38.5
= 4654.265 cm
2 Total area of the shaded parts
= 2 x (Area of the circle - Area of unshaded part)
= 2 x (4654.265 - 844.8825)
= 2 x 3809.3825
= 7618.765 cm
2 Answer(s): (a) 120.89 cm; (b) 7618.765 cm
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