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Getting Started - The Metric System
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The metric system uses 3 basic units to measure length, mass and volume.
We'll call these basic units root units.
Length, as we know, is how long something is.
Mass is how much stuff there is (like weight-see below*)
Volume is how much space something takes up.

The root metric unit for length is the meter (m).
The root metric unit for mass is the gram (g).
The root metric unit for volume is the liter (L).

A meter is about as long as a yard.
A gram is about the "weight" of a paper clip.
A liter is about 1 quart or 4 cups
The Metric System

Table: Root Units Used in the Metric System
What it Measures Description of Measurement Name of Root Unit Abbreviation About as Much as
Length how long meter m a yard
Mass how much stuff gram g a paper clip
Volume how much space it takes up liter L 4 cups or 1 quart

Note: Mass vs Weight:
You can think of the mass of an object as it's weight, though they are technically not the same. Mass is the amount of matter or stuff whereas weight is how strong gravity pulls on something. They're related because the more stuff you have, the more gravity pulls on it. How-ever, gravity depends on where you are, so things weigh less where there's less gravity (on the moon, for example). But mass remains the same wherever you are, because mass is the amount of stuff's and you have the same amount of stuff wherever you are. If this doesn't make sense, don't worry about it!
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