2004 AMC 10B Problem 15

Patty has 20 coins consisting of nickels and dimes. If her nickels were dimes and her dimes were nickels, she would have 70 cents more. How much are her coins worth?

\textbf{(A)}\ \$1.15\qquad\textbf{(B)}\ \$1.20\qquad\textbf{(C)}\ \$1.25\qquad\textbf{(D)}\ \$1.30\qquad\textbf{(E)}\ \$1.35

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