1.8 Values have units
Before I move on, let me explain the importance of using comments to record units of measurement.
Values are not just numbers, they have units: degrees Celsius, number of inhabitants, thousands of gallons, etc. Always make a note of the units the value refers to, using comments. This makes it easier to check whether the expressions are right. Disregarding the units will lead to wrong calculations and results.
Have you come across ‘horror stories’ that have happened due to mistakes in the unit of measurement?
Think through what happened and consider what you have learned from them.