Why are prefixes often added to si units?

Prefixes often added to S. I. units because this system is globally accepted

Explanation:

S.I. is abbreviation for international system. International system of units is globally accepted. Thus, on international platform all physical quantities should be represented in S.I. system of units.

There are 7 fundamental units in S.I system 2 supplementary and many derived units are included in S.I. system.

While using another system of units create confusion on international level. Thus, to avoid confusion all prefix are added to S.I. system.

to slow something down

Explanation: