Percentage Math

[Alvin777]

Hello Mac friends.

Supposing a 3.2 liter bottle is being compare to a 3.78 liter bottle (1 gallon) would you say:

the 3.2 liter has 18% less content than the one gallon one
or
the 3.2 liter has 15% less content than the one gallon one?

I ask coz' I'm trying to convince a seller, he shouldn't put 1 gallon in his product page description if his 99.90% or 99.99% IPA/isopropyl alcohol bottle is just 3.2 liters (not sure if there is 99.90% (amazing for cleaning USBs of all types and Thunderbolt and ports by spraying both the female part, the socket and the male part the cord or protrusion if it's a flashdrive, after also brushing w/ a toothbrush sprayed with the amazing 99.99% IPA).

 

[arw]

Definitely 15%. It all depends on the reference which is the value that follows the word "than".

3.2 has 15% less than 3.78 # |3.2-3.78| / 3.78=15.3%
3.78 has 18% more than 3.2 # |3.78-3.2| / 3.2=18.1%

Not sure I understand how that translates to your second question though…
A concentration of 99.99% means 1 unit consists of 99.99% pure alcohol and 0.01% neutral.
This emulsion can be sold per 1 gallon or 100 gallon - the concentration always remains 99.99%.

EDIT: Ah ok, I get it now. The seller actually ships 15% less product than advertised.
My second remark is irrelevant.