A cubic foot is 7.48 gallons, close enough to 7.5. 1 gallon of water is 8.33 lbs ≈ 25/3.
6 * 7.5 = 45 gallons
45 * 25/3 = 375 lbs -- easy mental math. Sure, the "accurate" answer is 373.87 lbs, but the aquarium probably isn't filled with distilled water, perfectly dimensionally accurate, or filled to that exact capacity.
Oh just wait until you see imperial hex screws. In metric you get them in screwdriver size relating to mm. US hex screws are like 16/64 of an inch or 5/16 of an apple. And of course they don't relate to metric at all and you can't use the same tools.
Or fucking AWG. Higher number means smaller diameter wire, and Americans are afraid of decimal or negative numbers so large diameters are 00, 000 etc. The formula is batshit insane
so people just use a lookup table.
Gauge is historically number of passes through gauging machine. With the machine and material in question being different for every single one. We took that and put it to a standard, so it's super messy and makes no sense.
I wonder how many people know these numbers. With the level of US education, probably 10%. Not to mention, most quantities will not be exact feet, more like 2'5". Good luck multiplying that, at least 74 cm is easy to type into a calculator.
Anyway, if you ask a European how much a liter of water weighs, 95% will say “a kilo” without much hesitation.
It's only arbitrarily easy since water has a density of 1 kg/l in metric, as it was designed to do so. If you happened to know the density of water is 62.2 lb/ft^3 then the equation is roughly 123*60 which is 360 lb. 372 if you can actually paid attention to what common core was trying to teach. If the material was anything other then water the math would be just as difficult to do in imperial or metric.
Metric is still far superior as the harmonized units make density in particular much easier to convert between. About the only thing imperial is better at is thread pitch of screws. I will also maintain that when describing human temperatures for weather Fahrenheit is a superior scale, but that's just more personal preference and experience then any rational basis.
It's only arbitrarily easy since water has a density of 1 kg/l in metric, as it was designed to do so.
it was designed to do so
That's also what we mean
I will also maintain that when describing human temperatures for weather Fahrenheit is a superior scale
That's one where I'd say it's almost entirely personal preference. Water freezing being at zero is handy because it's nice to know when there's ice/snow outside, but that's also something you could just learn to remember in Fahrenheit too. Doesn't really matter with that system. Kelvin and Celsius being bros is nice but it's extremely rare that I use that so eh.