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 Dec 7 comment Is there one method of adding and subtracting without a calculator? This method is just fantastically smart and yet not logically difficult, at least not how you explained it! Dec 7 awarded Critic Dec 6 comment Is there one method of adding and subtracting without a calculator? Yes, that is true. I've searched the internet, but I haven't found anything that isn't compiled, obfuscated and embedded in much other code so I can't extract it. + It is copyrighted.. Dec 6 accepted Is there one method of adding and subtracting without a calculator? Dec 6 comment Is there one method of adding and subtracting without a calculator? Thanks for your response! Actually, I'm asking this question because I'm making a computer method that is simply going to add, subtract, multiply and divide numbers. I need it because the language I'm writing in thinks any number greater than $9007199254740992$ is infinite. Great answer! Dec 6 comment Is there one method of adding and subtracting without a calculator? I agree with you on the multiplication/division, but not on the addition/subtraction. Dec 6 comment Is there one method of adding and subtracting without a calculator? @ChrisEagle I'm not an english speaker, so I'm not very experienced with english mathematical terms. Dec 6 comment Is there one method of adding and subtracting without a calculator? @HenningMakholm Exactly! I've already thought about this solution, but it again brings us back to start as you Henning stated. Dec 6 asked Is there one method of adding and subtracting without a calculator? Sep 29 accepted Why does this equation have different number of answers? Sep 28 comment Why does this equation have different number of answers? Please add your comments as an answers, as it is more useful for other people that come from Google. :) Sep 28 comment Why does this equation have different number of answers? @GerryMyerson But if there are "traps" like this, how does one discover them when the problems get more complex than just the simple problem I wrote? Sep 28 comment Why does this equation have different number of answers? @PeterTamaroff and Sep 28 comment Why does this equation have different number of answers? @PeterTamaroff I feel really stupid right now... I was just too caught up trying to make it become $x=2x$... Sep 28 comment Why does this equation have different number of answers? But then you can do $\frac{1}{x} = \frac{2}{x} | \times x$ and get $2=1$. Sep 28 comment Why does this equation have different number of answers? @PeterTamaroff Yes, now I see the problem! Thanks! I'm used to the fact that you can do anything to the x-es because you don't know what their value is. Sep 28 comment Why does this equation have different number of answers? Yes, you have done only thigs that are considered "legal", and you end up with an equation that is not equal to the one you started with, and you get an answer 0 that is not allowed in the first equation. So, are you saying that you cannot necessarily multiply the whole equation and get a new equation that is equal to the first one? Sep 28 comment Why does this equation have different number of answers? @GerryMyerson Could you please clarify a little bit? Sep 28 comment Why does this equation have different number of answers? @PeterTamaroff Ok, but how can they not be the same if I haven't done anything illegal? If they aren't the same, one can't put an equal sign between all the steps... Sep 28 asked Why does this equation have different number of answers?