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Silly question

  1. Dec 6, 2011 #1
    OK so this is probably a very silly and easy question...

    How do you say mathematically the amount that is in between to numbers?

    For example, between six and three, there are two numbers (4 and 5). But you dont say that it is the difference of 6 and 3, because that is saying 6 - 3 right? ... = 3.
  2. jcsd
  3. Dec 6, 2011 #2


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    Sorry to nitpick, but this is not true. There are a heck of a lot of numbers between 3 and 6: 3.5, 16/3, π, 5.714285714... the list goes on.
  4. Dec 6, 2011 #3


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    You are counting integers - a very small subset of numbers.
    The number of integers between 3 and 6 - exclusive of 3 and 6 - is 2.
    The number of integers between 3 and 6 - inclusive of 3 and 6 - is 4.
  5. Dec 6, 2011 #4


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    Are you looking for a formula? If n and m are integers with n > m then the number of integers strictly between them is n - m - 1.
  6. Dec 6, 2011 #5
    did u mean this... 3 < a < 6..? so that the number of a is 3 and 4..
  7. Dec 7, 2011 #6


    Staff: Mentor

    No. If a is an integer, then the two values that satisfy this inequality are 4 and 5. If a is a real number, then there are an uncountable infinity of numbers between 3 and 6.

    Also, please refrain from using "textspeak" such as u for you.
  8. Dec 7, 2011 #7
    ohh.. i see that..

    sorry for the inconvenience also..
    just a new member here..
  9. Dec 7, 2011 #8
    Hey sorry I guess I should have been more detailed. No, its not nitpicking. Yea Im talking about integers. Dave and Kurtz seem to be heading more in the direction that I wanted to.

    Excluding the two outside numbers, one would say there are two integers (ie whole units) in between 3 and 6. So again, how else do you say this this mathematically that is as natural and common as asking to someone to subtract lets say a price from the amount paid. I've noticed that the result is as Kurtz says...((n-m) -1), but im looking for a name for this value. The difference between n and m is , well, the difference, given by n-m. This "in between amount" thing is however n-m-1.

    Is it common to ask of such values? Where in life do you often want to know that kind of value?

    Thanks all.
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