2004 AMC 12A Problem 9

A company sells peanut butter in cylindrical jars. Marketing research suggests that using wider jars would increase sales. If the diameter of the jars is increased by 25\% without altering the volume, by what percent must the height be decreased?

\text {(A) } 10\% \qquad \text {(B) } 25\% \qquad \text {(C) } 36\% \qquad \text {(D) } 50\% \qquad \text {(E) }60\%

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