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Mathematical Proof Required

Posted by Karl Sharman on July 15, 2011 – 8:48 am

What unknown value can you add to 1 in order to get one less?

This post is under “Tom” and has 22 respond so far.
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22 Responds so far- Add one»

  1. 1. cazayoux Said:

    ‘get one less’ … than what? one less than 1? one less than the unknown value?

    1 + x = 1 – 1
    x = -1

    1 + x = x – 1
    1 = -1 … not possible

  2. 2. BearSprite Said:

    I could be oversimplifying here, but is the answer -1; ‘One less’ being equal to 0 and all.

    1 + x = 0
    x = -1

  3. 3. Karl Sharman Said:

    cazayoux, you are adding to one to get one less than one…

    BearSprite – this is me being picky, but I am looking for an unknown value – Minus 1 is kinda, well, y’know – known ;-)

  4. 4. Chris Said:

    When in Rome, do as the Romans do. X = 10, IX = 9.

  5. 5. Karl Sharman Said:

    Sorry Chris, but X isn’t 1. Good answer though, but like BearSprite’s answer, the I you are adding has a known value.

    Be prepared to send me straight to hell when you see the answer… This is a ToM question after all….

  6. 6. ibrahim Said:

    -1 is the correct answer.

  7. 7. ibrahim Said:

    1+iota sq.

    so basically iota square is the answer….

  8. 8. Rich Said:

    The Roman numeral X for 10. Add 1 and you get IX or 9.

  9. 9. Armeo Said:

    I think the key lies in interpreting “one less”. It could be -1, as that is one less than 0 which is a number one would normally use for comparing in addition or subtraction (just like 1 would be for division or multiplication). In a more relative sense, it could be 0, since that is one less than the number already used in the question, 1. Or it could be something entirely different.
    I don’t have an answer at the moment, actually. But I can at least say that 1,2,4,7,8 are not correct. :P

  10. 10. william Said:

    -1x where (x=1)

  11. 11. Karl Sharman Said:

    An unknown value implies a variable value.

    An actual number like -1 can’t be used since it is a known value. In mathematical notation the letter ‘n’ is used to denote an unknown/variable number.

    The variable ‘n’ can be added to the word ‘one’ to get ‘none’, which is one less than one.

    I’m going straight to hell for this one!!! In my defence, it was posted as a ToM question, not a Maths question….?

  12. 12. Chris Said:

    Hi Karl. LOL. I prefer x as the unknown value. That’s why I liked ix.

  13. 13. sandeep Said:


  14. 14. Karl Sharman Said:

    Sorry sandeep – ‘-2′ has a known value, and ‘-1′ is two less than one. Post 11. is the correct answer….

  15. 15. Ayush Said:

    Rich’s answer can also be taken as correct!!

  16. 16. Ayush Said:

    Hey, can anybody help me to register! The site is saying your registration is disabled!

  17. 17. Karl Sharman Said:

    Sorry Ayush – Rich is using known values! I = 1 and X = 10.

    You should be able to register under Blogroll on the right hand side of the site. If this isn’t working, try again in a few hours – there may be a glitch, also if you are using an newer Internet Explorer ensure the compatibility button is on….?

  18. 18. john Said:

    we add {+5-5} so we get one less

  19. 19. Sankalp Said:

    Listen man!!!! the square of “i” is the answer where “i”= square root of minus one!! as in imaginary no.!!! and It SEEMS “i” is UNKNOWN!! soo is it the answer….??

  20. 20. Chris Said:

    Peeps, Karl (the problem poster) has give the official answer in post 11.

    Sankalp, “i” (square root -1) is not unknown, so it doesn’t seem to be unknown either.

  21. 21. Reshma Said:

    -1 is the ans

  22. 22. rhiannon hoefer Said:




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