1950 AHSME Problem 31

John ordered 4 pairs of black socks and some additional pairs of blue socks. The price of the black socks per pair was twice that of the blue. When the order was filled, it was found that the number of pairs of the two colors had been interchanged. This increased the bill by 50\%. The ratio of the number of pairs of black socks to the number of pairs of blue socks in the original order was:

\textbf{(A)}\ 4:1\qquad\textbf{(B)}\ 2:1\qquad\textbf{(C)}\ 1:4\qquad\textbf{(D)}\ 1:2\qquad\textbf{(E)}\ 1:8

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