Metric Measurement: Length

Lesson Plan - Get It!

Audio:

• Did you know different systems of measurement are used in different parts of the world?

People in the United States, Liberia, and Myanmar use the customary system of measurement, that includes units such as feet, pounds, miles, and gallons. The rest of the world relies on the metric system of measurement, that includes meters, grams, and liters.

• So, why doesn't the United States use the metric system like the rest of the world?

Read Why Won't America Go Metric? (Time, John Bemelmans Marciano). After you read the article, tell your teacher or parent two reasons why the United States has not adopted the metric system.

The metric system is a system of measurement that revolves around decimals. You will learn more about how decimals are involved in the metric system in the final Related Lesson of this series, found in the right-hand sidebar.

As you move through these lessons, you will observe that, for each set of metric units (length, weight, volume), there is a root word, and you can change out the prefix at the beginning of the word to describe different measurements.

The prefixes for metric units are:

• kilo-
• hecto-
• deka-
• deci-
• centi-
• milli-

You will understand this concept better as you move through this lesson and look at different examples.

Like the customary system of measurement, metric units can be used to measure length, weight, and volume.

In this lesson, you will explore metric units of length.

• How would you describe length?

Length is the distance from one point to another. Length can be as short as the distance from your elbow to your shoulder, or as long as the distance from your house to France. Metric units of length are measured in meters.

You can add any of the prefixes listed in the paragraph above to describe different metric units of length, but the most commonly used metric units of length are millimeters, centimeters, meters, and kilometers.

A millimeter is very small. Ask your teacher or parent if you can see one of their credit or debit cards. The thickness of a credit or debit card is about one millimeter.

You are probably familiar with centimeters because centimeters can sometimes be found on rulers. Find a ruler in your house. One side should have inches.

• Does the other side of your ruler have marks, too?

If it does, these marks represent millimeters and centimeters. The diameter of a marble is about one centimeter. There are ten millimeters in one centimeter.

The next metric unit of length you need to know is a meter. Meters are used to measure medium and large distance, such as the size of a room in a house or the height of a tree. There are 100 centimeters in a meter.

• If there are 100 centimeters in a meter, how many millimeters are in one meter?

The last metric unit of length you need to know is kilometers. Kilometers are used to measure large distances, and are comparable to the customary unit of length, miles.

Kilometers are used to measure distances such as the distance from your house to the market, or the distance from London to Washington, D.C. There are 1,000 meters in one kilometer.

Copy the following chart onto a separate piece of paper:

As you watch Understanding mm, cm, m, and km, from Alex Lochoff, write the examples about when to use millimeters, centimeters, meters, and kilometers on the chart:

When you are finished listening to the song, add your own examples of length to your chart. Then, review your chart with a teacher or parent.

• Can they think of any examples that can be added to the chart?

You now know the metric units of length that are used most often. Move on to the Got It? section to practice using these measurements.