Natasha Arch Problem

We have a outer circle with a radius of 7.5m and an inner circle with a radius of  (7.5 -1.25) = (6.25)m

So the arc length of the outer circle = pi*(7.5)m   and the arc length of the inner circle is pi*(6.25)m

And the length of the 11 segments = 11*(1.25)m

So putting all these together, we have:

[pi(7.5 + 6.25) + 11*1.25] m =  about 56.95m = 57m  (rounded)