Answer
$\dfrac{41 \pi}{8} \ ft=5.125 \pi \ ft$
Work Step by Step
$l=\dfrac{\text{Measure of the arc}}{360^{\circ}} \times 2 \pi r ~~~(a)$
or, $l=\dfrac{\text{Measure of the arc}}{360^{\circ}} \times \pi d~~(b)$
Here, $r$ represents radius and $d$ is diameter.
We are given that the red arc measures $180^{\circ}+45^{\circ}=225^{\circ}$ and $r=4.1 \ ft$
Thus, equation (a) becomes:
$l=\dfrac{225^{\circ}}{360^{\circ}} \times 2 \pi (4.2)=
\dfrac{41 \pi}{8} \ ft=5.125 \pi \ ft$
