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13. The radius of a circle is 20cm. Thre...

13. The radius of a circle is 20cm. Three more concentric circles are drawn inside it in such that it is divided into four parts of equal area. The radius of the largest of the three concentric circles is

A

`(sqrt(2)-1)a`

B

`(sqrt(2)+1)a`

C

`(2+sqrt(2))a`

D

`(2-sqrt(2))a`

Text Solution

Verified by Experts

The correct Answer is:
B
It is evident from the Fig. 87 that the radius of the largest circle touching all the circles is
`OP_(1)=OC_(1)+C_(1)P_(1)=sqrt(2)a+a=(sqrt(2)+1)a`
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