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 Metric System:  A system of measuring lengths, volumes, and weights using units such as meter, liter, and kilogram.

The metric system is a system of measures based on powers of ten. The following are the fundamental units for the metric system:

  • meter, for length, abbreviated m
  • kilogram, for weight, abbreviated kg
  • liter, for volume, abbreviated L

Most countries in the world use the metric system because of its following features:

1. The fundamental unit, such as the meter, can be accurately reproduced without referring to a standard prototype. (A meter is defined to be 1,650,763.73 wavelengths of orange-red light in the spectrum of the element krypton 86 and can be reproduced in a laboratory anywhere.)

2. Units of the same type (i.e., length, weight, or volume) are related by simple decimal ratios. (For example, a centimeter is 100 times smaller than a meter, so 2.5 m = 250 cm.)

The following diagram is useful for converting units of length. Please note that each symbol is an abbreviation for length; notice the fundamental length, meter (m), is in the center. The units to the left are smaller than the units to the right. So a mm is smaller than a dm which is smaller than a km. To convert from, say, a decimeter (dm) to a hectometer (hm), count the number of spaces in between the units. Then, you only need to move the decimal to the left 3 times because you are changing from a smaller unit to a larger unit (we would move the decimal to the right if we were changing from a larger unit to a smaller unit). For example, 5000 dm is a length equal to 5 hm. If you had 100 km, how many cm would you have?

3. Different types of units for length, weight, and volume are defined in terms of each other. (For example, a liter is defined with reference to the meter: it is the volume of a cube that measures 10 cm (or 1 dm) on each edge. Thus, a liter can also be called a cubic decimeter.)