Attention Getting Question:
Why is it important to have a standard unit to measure length? Without standard units, measurements would be inconsistent.
A long time ago people would use their feet to measure things. But since people have different sized feet, people didn’t understand size or distance in the same way. So standard units of measurement were created. Today, there are two systems of measuring length: The metric system, and the U.S. Customary System.
Let’s look at the units of length in the Metric System. The smallest unit is the millimeter. The abbreviation or millimeter is mm. A millimeter is a very small distance. It is about the same as the thickness of a dime, or ten pieces of paper. The millimeter is used to measure very small distances such as an eyelash, a key on a keyboard, or your fingernail.
Next is the centimeter, or cm. The centimeter is equal to ten millimeters. A centimeter is about the width of your pinkie finger. The centimeter is also used to measure things such as the length of a laptop, the width of a table, or a person’s height.
The next common unit of length in the metric system is the meter, or m. One hundred centimeters is the same length as one meter, and because one centimeter is equal to ten millimeters, a meter is the same length as one thousand millimeters. A meter is about the distance from the floor to a doorknob. Meters are used to measure longer distances such as the height of a building, or length of a basketball court.
The longest unit in the metric system is the kilometer, abbreviated as km. The kilometer is equal to one thousand meters. Kilometers are used to measure distances between cities, or the depth of the ocean.
Now let’s look at the units of length in the US customary system.
The smallest unit is the inch. The inch is abbreviated as in. One inch is about the same as the width of your index finger when you bend it. The inch is used to measure objects like the size of a television, or the length of your pencil.
The foot (or ft) is the next unit. One foot is equal to twelve inches. A foot is about as long as piece of notebook paper. People use feet to measure their height, the length of a car, or even the height of a wall.
When you put three feet together you get a yard. A yard is equal to three feet, and because a foot is 12 inches, a yard is 36 inches. A yard is about the width of a door. Yards are used to measure distances such as football fields, and distances in races. The abbreviation for yard is yd.
The longest unit is the mile (or mi). The mile is equal to 5,280 feet or 1,760 yards. Like kilometers, miles measure distances between cities, and even the distance from the Earth to the moon.
There are many tools people use to measure length such as a ruler, meter stick, yard stick, tape measure, and even an odometer. A common tool used to measure smaller objects is the ruler.
Most rulers have two sides. One side has the metric system units in millimeters and centimeters and the other has US Customary System in inches.
When using a ruler to measure objects, make sure you line the object up with the zero to get an accurate measurement. This cell phone is ten centimeters long.
Sometimes the object is between two whole units. Here, the pencil is between the five and six; therefore its length is five and a half inches.
Let’s review units of length. The metric system consists of the millimeter, centimeter, meter, and kilometer. The U.S. Customary System consists of the inch, foot, yard, and mile. Use tools such as a ruler or tape measure to determine the length of various objects.