A) 4
B) 6
C) 8
D) 10
Correct Answer: C
Solution :
Radius of smaller ring = r units Radius of bigger ring = R units According to the question, \[2\pi R=3\times 2\pi r\] \[\Rightarrow \] \[R=3r\] Area of shaded part (path) \[=\pi {{R}^{2}}-\pi {{r}^{2}}=\pi {{(3r)}^{2}}-\pi {{r}^{2}}\] \[=9\pi {{r}^{2}}-\pi {{r}^{2}}=8\pi {{r}^{2}}\] \[\therefore \] \[8\pi {{r}^{2}}=n\,.\,n{{r}^{2}}\] \[\Rightarrow \] \[n=\frac{8\pi {{r}^{2}}}{\pi {{r}^{2}}}=8\]You need to login to perform this action.
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