How unfortunate

Doesnt the UK use a mix of both? Same as Canada?

US Customary Units and Imperial Units are not 100% the same, so calling the former the American system makes sense.

The UK is metrifing. But it takes time to make these shifts. Most hospitals will ask for weight in kg but usually have a calculator available. Charts and information leaflets have kg. Lift weight limits are in kg (usually then represend by people) Baby's weight is given in grams but usually the next question is what's that in old money. So the systems are all in kg but mentally we are in stones.

Liquids as in water specifically and not other liquids.

If by "metric system," you mean SI. But then, SI uses m^3^ for volume, not litres. The author didn't specify which metric system, so this could be valid.

“Better still learn mental math, you won’t always have an answer book in your pocket!” — 1500’s teachers

In the olden days sciencey types and engineers kept fact books listing such relations. They had a specific name that escapes me.

Likely a "CRC": CRC Standard Mathematical Tables, which is probably the same book as the pre-calculated mathematical operations you mentioned. It has a lot of good mathematical stuff in it such as basic formulas, trig functions, log tables, integral and differential functions, and formulas up through around Fourier analysis.

If we were doing that thought exercise where you can take a "go bag" back in time to build science up more quickly, a CRC and a slide rule would probably be in mine. I'd probably throw in a prism and as compact of a microscope that uses a mirror as a light source as I could get away with; both for showing small stuff living in water and for showing what couldn't be manufactured yet (depending on when I went back). I wouldn't waste space in the bag for anything dealing with the imperial system.

You know that water being exactly 1kg and 1l is specific to one pressure and temperature combination?

Metric is great for scientists in a lab with equipment to measure things.

Metric is just as great for everyday life as imperial units.

Also, a foot can be divided equally into 2, 3, 4, or 6 equally-sized pieces without resorting to estimation or irrational numbers; a meter cannot.

While I agree in principle, I also enjoy the chaos that imperial system causes when you try adding up 1 1/8 inches + 5 27/32 inches + 7 3/16 inches instead of just using decimal numbers.

Edited for clarity

Metric allows you to convert between length volume and mass in your head. Someone smarter than me could probably take a reasonable estimate of how long a kettle will take to boil just by knowing it's wattage and estimating its volume.

You're right that "pounds" may have e been a practical measurement back when people didn't have calibrated and everyone's hand weighed a pound. However, that advantage ceased once everyone standardised those measurements.

A metre is equally divisible by 50, 25, 20, 10, 5, and 2. There arr numerous advantages to a base 10 system.

The last bit of rationalizing is hilarious. It's like you don't even understand numbers or math, well what am I saying, you're an American

We can figure out what 70% of a meter is.

Good luck with your peasant system

"Decimalized currency is great for all those labcoats, but for us regular ol' normal folk, it's much easier to use real, easily divisible livres, which can be divided into 20 sous and subsequently into 12 deniers."

"In fact, imperial is so great because duodecimal invites so much divisibility! What's that? You're saying it goes 12 –> 3 –> 1760 for length, 16 –> 2000 for units of mass, that units of volume are a bastardized base-2 system where there isn't even a consistent multiple between units, and that pounds and short tons aren't cleanly divisible by 3? And that not a single unit of volume is divisible by 3 unless you bring it down to the level of teaspoons?"

"'Why not just switch to a fully duodecimal system if divisibility is so important to you', you ask? Well fuck you, a foot is about as long specifically as my forearm, and there's no way my poor, emaciated monkey brain would ever have found something similar to latch onto with SI units. Those people living in most of the rest of the world probably just carry meter sticks around up their asses. 'How many square inches is a 30 x 30-foot room?', you ask? Well fuck you again."

What do you mean you can not divide a meter without estimations or irrational numbers? Do you mean fractions or decimal? 1m/3=3.33… dm ( repeating, which means it is a rational fraction)

Every country used a system based off body parts or similarly easy-to-measure parts. When the metric system was invented, most of them switched because it was the logic thing to do. Some just decided that the dumb system was better who knows why.

Spain adopted the metric system in 1852 and by the time, they weren't the most advanced country.

Also, US Customary units share many of the same terms as Imperial, but the actual quantities differ.