A park is in the form of a square one of whose sides is

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A park is in the form of a square one of whose sides is 100 m . The area of the park excluding the circular lawn in the centre of the park is 8614 m². The radius of the circular lawn is ?

1. 21 m
2. 31 m
3. 41 m
4. None of these

Correct Option: A

Area of park = 100 x 100 = 10000 m²
Area of circular lawn = Area of park - area of park excluding circular lawn
= 10000 - 8614
= 1386

Now again area of circular lawn = (22/7) x r² = 1386 m²
⇒ r² = (1386 x 7) / 22
= 63 x 7
= 3 x 3 x 7 x 7

∴ r = 21 m