Because SI units are globally recognised (with the exception of Burma, Liberia and USA). SI stands for 'System International' See the related link to WIkipedia for more information.
SI units are used in Science Classes because they are universal and standard, and they are also easier to use because they are based no the power of ten.
Lots, but most people use only the Metric System.
Use the related link below to do this sort of conversion.
After converting all the measurements to the same units, you would use the Pythagoras Theorem.
Moles per litre, molL-1 and grams per litre, gL-1 are the most commonly used units, and are very easy to use when making measurements or conversions.
Measurements are made in units. The specific units that you would use depend upon what it is that you wish to measure. Practically anything can be measured.
Almost all scientists use metric units for scientific measurements.
Metric units of measurement are more fun to say.
SI units are used in Science Classes because they are universal and standard, and they are also easier to use because they are based no the power of ten.
They use scientific notation for very large or very small measurements
So that we all understand what we are doing.
Metric measurements use powers of 10 to create larger and smaller units.
Scientists usually use the metric system of measurement. This type has the words meter, liter, and gram. The SI system is in use by all engineers and scientists worldwide. Among the base units from which all other units are derived are; Length Metre Mass Kilogram Time Second
mm (millimeters)
Sort of. US measurements are now for the most part defined in terms of SI units. Also, a few SI units such as "seconds" are used directly.
If they are sensible, they will use those units defined and agreed by the International Standards Organization (ISO), as these will be universally understood and normally are required to be used in scientific publications.
The same units that you use for length and distance. For example, the SI unit would be the meter.