How to solve word problems when mixing two quantities with different prices.
The laws of physics are not affected by varying amounts of inertia.
How to compute the average rate of change of the amount of a drug in a patient's bloodstream over an interval of time, and how to interpret whether the amount is increasing or decreasing over time.
How to solve an interest problem when given the total amount deposited.
Using specific heat to predict the amount of heat absorbed or released in reactions.