2009 AMC 10A Problem 18

At Jefferson Summer Camp, 60\% of the children play soccer, 30\% of the children swim, and 40\% of the soccer players swim. To the nearest whole percent, what percent of the non-swimmers play soccer?

\mathrm{(A)}\ 30\% \qquad \mathrm{(B)}\ 40\% \qquad \mathrm{(C)}\ 49\% \qquad \mathrm{(D)}\ 51\% \qquad \mathrm{(E)}\ 70\%

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