Question

15 . Find the area of the region between two concentric circular paths. If the radii of the circular paths are 210m and 490m respectively.

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Answer 1

Answer:

Let the radii of the outer and inner circles be r

2

and r

1

respectively; we have

Area=πr 2

2 −πr 12 =π(r 22 −r 12 )=π(r 2 −r )(r

2

+r

1

)

=π(5.7−4.3)(5.7+4.3)=π×1.4×10 sq. cm

=3.1416×14sq.cm.=43.98 sq. cm