Editing Ratio (section)

==Units==
Ratios may be [[Dimensionless quantity|unitless]], as in the case they relate quantities in units of the same [[dimensional analysis|dimension]], even if their [[units of measurement]] are initially different.
For example, the ratio {{nowrap|one minute : 40 seconds}} can be reduced by changing the first value to 60 seconds, so the ratio becomes {{nowrap|60 seconds : 40 seconds}}. Once the units are the same, they can be omitted, and the ratio can be reduced to 3:2.

On the other hand, there are non-dimensionless quotients, also known as [[rate (mathematics)|''rates'']] (sometimes also as ratios).<ref>{{cite book |quote="Velocity" can be defined as the ratio... "Population density" is the ratio... "Gasoline consumption" is measure as the ratio... |title=Ratio and Proportion: Research and Teaching in Mathematics Teachers |year=2012 |publisher=Springer Science & Business Media |url=https://books.google.com/books?id=eawKLY71xvkC&q=perspective&pg=PA25 |author1=David Ben-Chaim |author2=Yaffa Keret |author3=Bat-Sheva Ilany|isbn=9789460917844 }}</ref><ref>''"''Ratio as a Rate''. The first type [of ratio] defined by [[Freudenthal]], above, is known as rate, and illustrates a comparison between two variables with difference units. (...) A ratio of this sort produces a unique, new concept with its own entity, and this new concept is usually not considered a ratio, per se, but a rate or density."'', "Ratio and Proportion: Research and Teaching in Mathematics Teachers" [https://books.google.com/books?id=eawKLY71xvkC&q=rate&pg=PA29]</ref>
In chemistry, [[Mass concentration (chemistry)|mass concentration]] ratios are usually expressed as weight/volume fractions.
For example, a concentration of 3% w/v usually means 3&nbsp;g of substance in every 100&nbsp;mL of solution. This cannot be converted to a dimensionless ratio, as in weight/weight or volume/volume fractions.