Metric Units of Length
Metric units of length form a base-ten measurement system used worldwide: 10 millimeters (mm) = 1 centimeter (cm), 100 centimeters = 1 meter (m), and 1,000 meters = 1 kilometer (km). In 4th grade math with Saxon Math Intermediate 4, Chapter 2, students learn these conversions and apply them to real-world contexts — a table might be 2 meters (200 cm) and a race might be 5 kilometers (5,000 m). The metric system's base-ten structure makes conversions much simpler than US customary units and is the universal system used in science worldwide.
Key Concepts
Property A measurement system used worldwide, based on powers of ten. Key facts: 10 millimeters = 1 centimeter, 100 centimeters = 1 meter, and 1000 meters = 1 kilometer.
Examples A table that is 2 meters long is $2 \times 100 = 200$ centimeters long. A 5 kilometer race is $5 \times 1000 = 5000$ meters long.
Explanation This system is logical, like money! Ten millimeters form a centimeter, 100 centimeters make a meter (think cents in a dollar), and 1000 meters create a kilometer. This base ten structure makes converting between units a breeze and is used globally, especially in science.
Common Questions
What are the metric units of length in order from smallest to largest?
Millimeter (mm), centimeter (cm), decimeter (dm), meter (m), kilometer (km). The most commonly used are millimeter, centimeter, meter, and kilometer.
How many centimeters are in a meter?
There are 100 centimeters in 1 meter. This is similar to cents and dollars: 100 cents equal 1 dollar. So 3.5 meters = 350 centimeters.
How many meters are in a kilometer?
There are 1,000 meters in 1 kilometer. A kilometer is the metric unit for measuring long distances, like a running race or the distance between towns.
How many millimeters are in a centimeter?
There are 10 millimeters in 1 centimeter. Millimeters are used for very precise, small measurements like the thickness of a coin or a paper clip.
When do 4th graders learn metric units of length?
In Saxon Math Intermediate 4, Chapter 2, Lessons 11-20, metric units of length are introduced alongside US customary units as part of a broader measurement unit.
Why is the metric system easier for conversions than US customary units?
The metric system is entirely base-ten, so converting between units only requires multiplying or dividing by 10, 100, or 1,000. US customary conversions use irregular factors (12 inches per foot, 3 feet per yard), making them harder to remember.