# Question #cb4c0

Nov 1, 2016

See explanation.

#### Explanation:

Probaby you wanted to ask why scientists use SI units instead of units like inches ans gallons.

The reason can be that the definition and value of all SI units is the same in every part of the world while other units may have different values.

For example let's take gallon.

It can have 3 different values depending on country (US or UK) and the thing you measure (there is a measure called US dry gallon for solids and US liquid gallon for liquids).

• Imperial gallon $1 g a l = 4.54609 l$

• US liquid gallon $1 g a l = 3.78541 l$

• US dry gallon $1 g a l = 4.404884 l$

From this you can say that a gallon can be either less than $4.5 l$ (US gallons) or more than $4.5 l$ (Imperial gallon).

So to avoid any possible misunderstanding scientists chose an international system of units SI.