1950 AHSME Problem 34

When the circumference of a toy balloon is increased from 20 inches to 25 inches, the radius is increased by:

\textbf{(A)}\ 5\text{ in}\qquad\textbf{(B)}\ 2\frac{1}{2}\text{ in}\qquad\textbf{(C)}\ \frac{5}{\pi}\text{ in}\qquad\textbf{(D)}\ \frac{5}{2\pi}\text{ in}\qquad\textbf{(E)}\ \frac{\pi}{5}\text{ in}

Full credit goes to MAA for authoring these problems. These problems were taken on the AOPS website.