## Why are units required to express the amount of a quantity?

Units are required to express the amount of a quantity because they provide a standard of measurement that allows us to compare and communicate measurements effectively. Without units, it would be difficult to know what someone means when they say they have a certain amount of something.

For example, if someone says they have a mass of 10, it’s not clear what units they are using to express that measurement. It could be 10 grams, 10 kilograms, or even 10 pounds. However, if someone says they have a mass of 10 kilograms, then it is clear what the measurement is referring to and it can be compared with other masses measured in kilograms.

Units also allow us to perform calculations with quantities expressed in different systems of measurement. For instance, if we need to add two lengths together, but one is measured in inches and the other is measured in centimeters, we need to convert one of the measurements to a common unit (such as meters) before we can perform the calculation.

Furthermore, units also enable us to check the dimensional consistency of equations, ensuring that the units on both sides of the equation match. This is a crucial part of scientific and engineering calculations to avoid errors and ensure accurate results.