What units of measurements did the scientists, in 1875 from 17 countries, agree to use to communicate with one another.

SI units are significant because they are mutual to the people of the entire world, so that people from different countries can communicate with each other appropriately regarding trade and science.  

It makes methodical use of prefaces, making it easy to express very large or very small numbers.

A prefix is fragment of the unit, and its symbol is written initially to a unit and few units are undergoing improvisation as per the requirements of the present day.  

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