Stadium Seating A circular stadium consists fo 11 sections with aisles in between. With 13 tiers of concrete steps for the final section, section K. Seats are places along every concrete step, with each step 0.45 m wide. The arc AB at the fron of the first row is 14.4 m long while the arc CD at the back of the back row is 20.25m long. 
1. How wide is each concrete step?
2. What is the length of the arc of the back of row 1, row 2, row 3, and so on?

If the inner radius of row $i$ is $r_i$, then the arc length of the inner arc of that row is given by 
$$L_i = \frac{2\pi r_i}{11}.$$
If the width $w$ of each step is constant, then
$$r_i = r_1 + (i-1)w$$
and the arc length of the outer arc of step $i$ is
$$M_i = \frac{2\pi (r_i+w)}{11}.$$
You now have two unknowns -- $r_1$ and $w$ -- and two equation relating the unknowns to known quantities, namely $L_1$ and $M_{13}$. Solve for $w$ and $r_1$ and then plug into the equation above to find $M_i$.
