The circumference of a circle is $100$ inches. The side of a square inscribed in this circle, expressed in inches, is:
$\textbf{(A) }\frac{25\sqrt{2}}{\pi}\qquad \textbf{(B) }\frac{50\sqrt{2}}{\pi}\qquad \textbf{(C) }\frac{100}{\pi}\qquad \textbf{(D) }\frac{100\sqrt{2}}{\pi}\qquad \textbf{(E) }50\sqrt{2}$
First, find the diameter of the circle.  Plug in the circumference for the formula $C = \pi d$ to solve for $d$.
\[100 = \pi d\]
\[d = \frac{100}{\pi}\]
Since all of an inscribed square's vertices touch the circle, and one of the angles of the circle is $90^{\circ}$, the square's diagonal is the diameter of the circle.

From the Pythagorean theorem (or 45-45-90 triangles), the side length is $\frac{50\sqrt{2}}{\pi}$ inches, which is answer choice $\boxed{\textbf{(B)}}$ .