The dosage of a certain medicine for a child is 2.5mL for each 3 kg mass of the child .What is the dose, in milliliters, for a child with a mass of 16.5 kg?
Common: this question seems want to ask students to solve a ratio problem using proportional reasoning. The intended answer will be
The dose for a child with a mass of 16.5 kg is equal to
2.5mL *(16.5kg/3kg) =2.5mL*5.5=13.75mL
However, this answer ignore an important fact that the dosage of a certain medicine for a child is not proportional (or linear) to the mass of the child. Children are not small adults, their bodies respond to medicines differently. They need medicines tailored to their age, body weight and physiological condition. In fact, blindly applied the above dosage of medicine to any child could cause fatal incident.
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