Two concentric circles form a ring. The inner and outer circumferences of ring are 5187 m and 3527 m respectively. Find the width of the ring.

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

Then   $2\mathrm{\pi R}=\frac{352}{7}=>R=\frac{352}{7}*\frac{7}{22}*\frac{1}{2}=8m$ 

  $2\mathrm{\pi R}=\frac{528}{7}=>R=\frac{528}{7}*\frac{7}{22}*\frac{1}{2}=12m$

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