Question

A children's liquid medicine contains 100 mg of the active ingredient in 5 mL . If a child should receive 150 mg of the active ingredient, how many milliliters of the medicine should the child be given? For the purposes of this question, assume that these numbers are exact.

Answer 1

Answer:

The correct answer is 7.5 ml

Explanation:

The medicine contains 100 mg in 5 ml, that means that the concentration of the active ingredient is 100 mg/5 ml= 20 mg/ml

If we divide a concentration (in mg/ml) into a mass (in mg) we obtaine a volume (in mL). Thus, in order to calculate the mililiters of medicine which contain 150 mg of the active, we have to only divide mass (150 mg) into the concentration of active ingredient as follows:

mL = $\frac{150 mg}{20 mg/mL}$= 7.5 mL