GMAT scale factors Percent Increases and Decreases

題目:
For a certain cylinder, the diameter equals the height. If every length in this cylinder is decreased by 60%, then to the nearest integer, by what percent does the volume decrease?
(A) 22%
(B) 40%
(C) 60%
(D) 84%
(E) 94 %

GMAT scale factors Percent Increases and Decreases