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  • File : 1328266950.gif-(4 KB, 547x83, 20120203.gif)
    4 KB mathfag !lBA0pEMs2M 02/03/12(Fri)06:02 No.4325322 sticky  
    O say does that math-spangled banner yet wave
    >> mathfag !lBA0pEMs2M 02/03/12(Fri)06:21 No.4325350
    1994 m / (1993*1994) < k / n < (1993 m + 1993)/(1993*1994)
    and so there are gaps; those gaps are 0 to 1993, 1994 to 3986, ... 1993^2 - 1, 1993^2
    so for one, n must be at least 1993 for there to be one k/n in each of 1992 gaps between 0 and 1.

    Also, n can't be 1993 or 1994, because then k/n would fall on m/1993 or (m+1)/1994
    >> mathfag !lBA0pEMs2M 02/03/12(Fri)06:34 No.4325375
    I feel like shit, though, and while you don't give half a damn hairy rat's ass, I am going to stop working on this problem on account of having the flu.
    >> Anonymous 02/03/12(Fri)08:01 No.4325482
    >>4325322
    I've thought about the problem, I see some properties, but as to how to actually find such n is beyond me.
    >> Anonymous 02/03/12(Fri)08:03 No.4325487
    >>4325482
    For the record, we can ignore any answer larger than 3987. It's obvious that if n = 3987, then it works for k = 2m.
    >> TN5 !/sci/TN5.. 02/03/12(Fri)08:06 No.4325495
    Bounding from the other side:
    n1993+1994
    If n1993+1994, then we take k = 2m+1 and
    m1993=2m1993+19932m+11993+19942m+21994+1994=1994m+1
    >> TN5 !/sci/TN5.. 02/03/12(Fri)08:07 No.4325496
    >>4325487
    Ah, you beat me to it.
    >> Anonymous 02/03/12(Fri)08:11 No.4325503
    >>4325496
    Except that I said k=2m, which indeed should be k=2m+1. Cheers
    >> Anonymous 02/03/12(Fri)08:12 No.4325505
    3987 is the solution.
    >> Anonymous 02/03/12(Fri)08:13 No.4325506
    >>4325505
    It's only the solution, if there is some kind of proof that it's the smallest.
    >> TN5 !/sci/TN5.. 02/03/12(Fri)08:16 No.4325512
    >>4325505
    Yeah I would also think that. But now we have to prove it. I agree that if it's not that, then the gaps will most likely not all be "aligned" properly and some values will fall between a m+11994 and then next m+11993.
    >> Anonymous 02/03/12(Fri)08:37 No.4325556
    >>4325322
    >>4325512

    for(int n = 1992; n < 4000; n++) {
    boolean b = true;
    for(int m = 1; m < 1993 && b; m++) {
    int k = (m*n)/1993 + 1;
    if (k*1994 >= ((m+1)*n)) {
    b = false;
    }
    }
    if (b) {
    System.out.println("Answer:" + n);
    break;
    }
    }
    It outputs 3987.
    It's an ugly proof, but a proof
    >> TN5 !/sci/TN5.. 02/03/12(Fri)08:40 No.4325560
    >>4325556
    Works for me. Having the non-computationally-challenging proof would be nice, though.
    >> Anonymous 02/03/12(Fri)08:41 No.4325565
    Assume 1995 =< n < 1993 + 1994

    For every legit k,

    k/n < (n-1)/n < 2*1993/(1993+1994)
    k/n >= 3/n > 3/(1993+1994) = 1/(3*443) = 1/1329

    So: 1/1329 < k/n < 2*1993/(1993+1994) for every k.

    Not sure if this helps.
    >> Anonymous 02/03/12(Fri)08:46 No.4325579
    >>4325565
    Derp, plugged in the wrong values
    >> Anonymous 02/03/12(Fri)08:47 No.4325585
    >>4325556
    Let n be any number between 1994 and 3986.
    Look at the case where m = 1992.
    Since n <= 2*1993, we can see that in those cases, k must be equal to n-1. However, n-1/n >= 1993/1994, if n >= 1994.
    Hence, we reach contradiction.
    >> TN5 !/sci/TN5.. 02/03/12(Fri)08:54 No.4325608
    >>4325585
    Sounds right to me. We haven't forgotten anything, have we?
    >> Anonymous 02/03/12(Fri)09:02 No.4325640
    Why must k=n-1?
    >> TN5 !/sci/TN5.. 02/03/12(Fri)09:03 No.4325645
    >>4325640
    Because otherwise the left does not hold.
    >> Anonymous 02/03/12(Fri)09:05 No.4325651
    >>4325645
    Oh, fair enough
    >> mathfag !lBA0pEMs2M 02/03/12(Fri)09:12 No.4325674
    >>4325608
    Nope, that's just what I was thinking of. We know it can't be smaller than 1993, and we know it can't be at least 1993 but smaller than 3987, and we know it can't be larger than 3987.



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