AHSME 1950 Problem 22

Successive discounts of $10\%$ and $20\%$ are equivalent to a single discount of: $\textbf{(A)}\ 30\% \textbf{(B)}\ 15\% \textbf{(C)}\ 72\% \textbf{(D)}\ 28\% \textbf{(E)}\ \text{None of these}$