[metaphor]

Now change that first number from 6.112 to 6.789 and watch that same child stumble.

I've always found it curious how Europeans pride themselves in speaking their native tongue + English...except its always a cultural flame war-inciting impediment when the communication barrier involves a mere arithmetic unit conversion. Doubly ironic when most of the world is consciously aware of what the prevailing USD exchange rate with their native currency is without complaint, whereas the average American simply doesn't have a clue how many Euros a US dollar gets them.

Similarly, if the Brits want to reference weight in stone, or Canadians want to sell me lumber in board-foot, I don't find that offensive in the least; I'm of the position that the impetus is on me to understand their measure, not for the one communicating to conform to my norms.

[slau]

Why would there be any stumbling? Because it's two 6s? Because there's two carries?

[metaphor]

The child would clearly have to mentally carry four times all the way down the chain:

    11 11
    14.446
  +  6.789
  --------
    21.235

[delta_p_delta_x]

Really, this is primary school maths. I learnt about carries when I was seven.

Every single thread (both here and on Reddit) I've seen says 'oh, decimals are too hard'.

This is a terrible indictment of the American schooling system if your only defence against metrication is 'I can't do decimals'. It is you lot who have to catch up.

[metaphor]

> This is a terrible indictment of the American schooling system if your only defence against metrication is 'I can't do decimals'. It is you lot who have to catch up.

To the contrary, if you read into the full context of this thread, the underlying contention isn't that we're incompetent at decimal arithmetic, but that the rest of the world (and apparently some Americans too) believes our common fractional arithmetic is too much of a mental burden, and I don't blame those individuals either.

Indeed decimal arithmetic is trivial to most grown adults, but that wasn't the point; the example was merely to highlight how just slightly changing a few numbers in the same sequence of operations serves as an effective counterpoint to the grandparent's assertion that "even children can do in their head reliably".

Americans are taught and handle metric units in compulsory school just fine, but most of us also practice imperial units on a daily basis as well. We're just not culturally predisposed to complain when everyone else conveys measure in the SI mks/cgs framework.

[delta_p_delta_x]

> common fractional arithmetic

I agree with the current of the thread, that mixed numbers are decidedly inferior to decimals. They're not harder, strictly speaking, but are more tedious, and this additional tedium introduces steps that people can make mistakes in. Fractions are also not easily parsed by standard desk calculators, and are not easily printed in a single line. They may even be mistaken by someone in a hurry as three separate numbers.

Decimals do away with all this unnecessary pain, and this really is the key point of metrication: it is a waste of time and effort to use non-SI units and convert back and forth or deal with mixed numbers. That's what people are complaining about: it is exasperating when Americans dredge mediæval units up in the 21st century, when we have a modern, simple, and unified system of units available.

[metaphor]

> ...mixed numbers are decidedly inferior to decimals. They're not harder, strictly speaking, but are more tedious, and this additional tedium introduces steps that people can make mistakes in.

A counterpoint to this is the fact that there are close to a million employed carpenter tradesmen in the US whose average level of education is a high school diploma[1], and yet their trade operates almost exclusively on fractional arithmetic, most of which occurs mentally on the jobsite.

The point being that tedium is a relative measure of training and experience, and it goes without saying that those trained in only decimal form are liable to struggle with unfamiliar systems.

And if you think that's bad, try purchasing lumber from any lumber yard in Canada or the US; the trade's board-foot system[2] will really tickle your metric attachment.

> it is a waste of time and effort to use non-SI units and convert back and forth.

It seems the story is more like it's a waste of time to those who find value in what Americans have to say but are unaccustomed and insistently resistant to performing conversions. I don't disagree that there's certainly value in having a globally common measurement framework, and indeed an American who conveys imperial units in a European setting is liable to be chastised. But old habits die hard and last time I checked, we're not having this discussion on a .eu gTLD.

Now try imagining how the typical American feels when engaging with the rest of the world: SI units, (,) and (.) symbols reversed, left-lane driving, etc. We tend to just adapt.

[1] https://www.bls.gov/ooh/construction-and-extraction/carpente...

[2] https://en.wikipedia.org/wiki/Board_foot

[allarm]

What’s so difficult with that? Just use pen and paper for calculations, you’re supposed to write down the result anyway. It’s a simple math.

[metaphor]

The goalposts set by the grandparent was reliable mental arithmetic by a notional child:

> ...which probably even children can do in their head reliably.

You're moving the goalposts.

An indefinite number of applications exist where we can make meaningful decisions all day without ever needing to write results down.