Bunuel wrote:

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 should the prescribed dosage be reduced to bring it down to the typical dosage?

(A) 7.5

(B) 9.0

(C) 11.1

(D) 12.5

(E) 14.8

Typical dosage is \(2\) cubic centimeters per \(15\) pounds \(= \frac{2}{15}\)

Let the typical dosage be \(x\) cubic centimeters for \(120\) pounds \(= \frac{x}{120}\)

\(\frac{2}{15} =\frac{x}{120}\)

\(x = \frac{2*120}{15} = 16\)

Therefore typical dosage for \(120\) pounds is \(16\) cubic centimeters.

Doctor prescribed \(18\) cubic centimeters for \(120\) pounds.

Difference \(= 18 - 16 = 2\)

We need to find the difference ie; \(2\) is what percentage of the dosage doctor has prescribed \(18\).

Required percent \(= \frac{2}{18} * 100 = 11.1\) .

Answer (C)...