[求助]一道数学题

A doctor prescribed 18 cubic centimeters of a certain drug to a patient whose body weight was 120 pounds. If the typical dosage is 2 cubic centimeters per 15 pounds of body weight, by what percent was the prescribed dosage greater than the typical dosage?

Answer:12.5

你看看這種算法對不對

每15 pound 用 2 cubic cm 的藥量

所以120 pound 應用 120/15=8 8*2=16 cubic cm 的藥量

但醫生開了18 cubic cm, 所以多開的要量比正常藥量多出了 [(18-16)/16]*100%=12.5%

歡迎指教