Primary Mathematics/Metric system

The metric system, originating in France in 1791, is the current international standard for measurements. In common use, there are three units that are frequently used in the metric system:
 * Meter (m) - a unit of length
 * Gram (g) - a unit of mass
 * Liter (L) - a unit of weight

The two tangible units, meter and gram, can be converted to larger and smaller representations simply by multiplying by 10.

Meter
A meter is the standard unit of length; it is approximately equal to 39.37 inches (3.28 feet) in the US customary system.

A normal meter stick will have 10 divisions, each representing 1 decimeter (dm). This is further divided by 10 to give a total of 100 centimeters (cm), and then by ten again to give 1000 millimeters (mm).

1000 meters equals 1 kilometer (km).

In the UK a meter is known as a "metre".

Gram
The gram is a unit of mass. It is commonly used to state weights as well.

There are 1000 grams in a kilogram (kg).

1000 kilograms is equal to 1 tonne (t).

A milligram (mg) is 1/1000th of a gram. Milligrams are often used in medicine and chemistry.

Liter
The liter (L) is a unit of liquid volume, equal to a cube of water measuring 10cm * 10cm * 10cm. A milliliter (mL) is equal to one cubic centimeter.