Chapter 1
Number and Quantity
Course: Core Academic Skills For Educators Combined Test 5752
Subject: Core Academic Skills Educators Mathematics 5733
Chapter: Number And Quantity
1. Understanding Units and Measurements
A unit is a standardized quantity used to measure and express a physical property. Without units, a measurement has no context. For example, saying a table is “2 long” is meaningless without specifying “2 meters” or “2 feet.”
Measurement is the process of assigning a number to a physical quantity using a chosen unit as a reference. The same physical quantity can be expressed in different units, and in many real-life situations, it is necessary to convert between these units for communication, consistency, or compatibility with formulas.
There are two main systems of measurement used globally:
- The metric system (International System of Units, or SI) is based on powers of ten, making conversions straightforward by multiplying or dividing by factors of ten. Units include meters for length, liters for volume, and grams for mass.
- The U.S. customary system uses units such as inches, feet, yards, miles, ounces, pounds, and gallons. Conversions within this system rely on fixed, memorized relationships that are not based on powers of ten.