Two concentric circles form a ring. The inner and outer circumferences of ring are \(\frac{518}7\) m and \(\frac{352}7\) m respectively. Find the width of the ring.

A 4

B 5

C 6

D 7

Correct Answer: Option A

Let the inner and outer radii be r and R metres.

Then \(2\mathrm{πR}=\frac{352}7=>\mathrm R=\frac{352}7\ast\frac7{22}\ast\frac12=8\mathrm m\)

\(2\mathrm{πR}=\frac{528}7=>\mathrm R=\frac{528}7\ast\frac7{22}\ast\frac12=12\mathrm m\)

=> Width of the ring = (R - r) = (12 - 8) m = 4 m.