2

I ask my german friend a math question:

I expected my German friend to answer it as this: $$1.000 - 1 = 0$$ $$1{,}000 + 1 = 1{,}001$$ but instead my German friend says this: $$1.000 - 1 = 999$$ $$1{,}000 + 1 = 2{,}000$$

All of my German friend said this, which isn't correct. Why do so many Germans think that 1.000 - 1 = 999? He said he's good at math so why does he thinks that 1.000 - 1 = 999?

5th grader math kid5
  • 21
  • 4
    , and . are different notations for decimals in different countries. – I was suspended for talking May 16 '20 at 20:04
  • 1
    That's because in Europe they use comma as a separator for fractional part. – Vasili May 16 '20 at 20:04
  • 2
    Welcome to Math SE. Some countries use alternate symbols for the thousands and decimal separators than others. For example, Countries using decimal comma shows Germany being one of the countries, among many others, which use a decimal comma. – John Omielan May 16 '20 at 20:05
  • In Germany (and, I think, in many European countries) the decimal point sign is "," and the mark you put between blocks of 3 digits is ".". I learned this the hard way when I studied math in Germany in 4th grade. – kimchi lover May 16 '20 at 20:06
  • 1
    "He said he's good at math so why does he thinks that 1.000 - 1 = 999?" Because he is good at math and knows that one thousand minus one is $999$. Why do you think that one thousand minus one is zero? That makes no sense! Are you bad at math?.... See what I did there? ...Germans don't think one minus one is $999$. Germans think $1.000$ is one thousand and $1,000$ is one. And Americans think the exact opposite. So which one is right and which one is wrong. And why? .... Neither is right or wrong and the only way you can say one is right or wrong is what your teacher tells you. – fleablood May 16 '20 at 20:29
  • The german word for "poison" is "gift". So if you gave your german friend a christmas present would he accuse you of trying to kill him. No. Because although "gift" means poison to him it means present to you. Which one of you is right or wrong. Neither of course. So you german friend thinks "one thousand" is $1.000$ and $1.000 -1= 999$". You think "one thousand" is $1,000$ and $1,000 -1 =999$. Meanwhile my ancient Roman friend thinks "one thousand" is $M$ and $M-I=CMXCIX$. Which one is right or wrong. Neither of course. – fleablood May 16 '20 at 20:39
  • @kimchilover: I can assure you that the reverse is much much harder ! even because after the comma/point come the inches- psi - BTU etc. – G Cab May 16 '20 at 22:39
  • @GCab I believe you. And then there is our spelling, too. However: I found handwritten Fraktur a bit much. – kimchi lover May 16 '20 at 23:18

1 Answers1

4

When writing numbers, Germans use the periods and commas the way Americans use commas and periods, respectively. Germans write $1.000$ for our $1,000$ and $2,000$ for our $2.000$. Their $1.000-1=999$ means exactly the same thing as our $1,000-1=999$, and their $1,000+1=2,000$ means exactly the same thing as our $1.000+1=2.000$.

Wikipedia has an article on various national usages of the decimal separator and thousands separator. Americans use the period for the former and the comma for the latter; Germans (and many others, including most of Europe) reverse this.

Brian M. Scott
  • 616,228