1951 AHSME Problem 13

A can do a piece of work in 9 days. B is 50\% more efficient than A. The number of days it takes B to do the same piece of work is:

\textbf{(A)}\ 13\frac {1}{2} \qquad\textbf{(B)}\ 4\frac {1}{2} \qquad\textbf{(C)}\ 6 \qquad\textbf{(D)}\ 3 \qquad\textbf{(E)}\ \text{none of these answers}

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