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Hardcore Maths Question

Scheduled Pinned Locked Moved Algorithms
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  • I Ingo

    ((3628799 + 1) / 10) / (2 * 3 * 4 * 6) + (9 - 7 + 8 - 10) + 1 = 2519. ;)

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    User 12346520
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    • J JenovaProject

      10! - 1 = 3628799. Its 1 less than a multiple of 1, 2, 3 ... 10.

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      • R Raj Lal

        its the LCM of all the numbers (2520) - 1

        Omit Needless Words - Strunk, William, Jr.


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        • J Jon Sagara

          N(1) = 2519 N(2) = 2519 + 2520 = 5039 N(3) = 2519 + 2520 + 2520 = 7559 N(4) = 2519 + 2520 + 2520 + 2520 = 10079 ... N(n) = 2519 + (n - 1)*(2520) No idea what the heck it means, though. Care to enlighten us mathematically-challenged folks?

          Jon Sagara When I grow up, I'm changing my name to Joe Kickass! My Site | My Blog | My Articles

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          • J Judah Gabriel Himango

            Quartz... wrote:

            It's the journey, not the destination

            Very true. I actually had fun writing a little piece of code to solve it, though, so it was the journey even still. :) I added some more code that added each match to a list box on a Windows Form. Then, after seeing how it froze up the UI, I did it on a background thread. Still, the UI thread would get flooded with matches, almost preventing it from painting, so I further chagned the code to only update during app idle. Voila, cool little WinForms program that solves it. :cool:

            Tech, life, family, faith: Give me a visit. I'm currently blogging about: Messianic Instrumentals (with audio) The apostle Paul, modernly speaking: Epistles of Paul Judah Himango

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            • L leppie

              Some other interesting and useless observations:

              1*2*3*4*5*6*7*8*9 is divisible by 2520 = 144
              2520 is divisible by 2 * 3 * 5 * 7 = 12 (product of prime 1 - 9)
              4 * 6 * 8 * 9 is divisible by 144 = 12 (product of 'non' prime 1 - 9)

              :doh:

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              • L leppie

                Jon Sagara wrote:

                N(n) = 2519 + (n - 1)*(2520)

                N(n) = (n * 2520) - 1 = 2520n - 1

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                • P Paul Conrad

                  Judah Himango wrote:

                  Voila, cool little WinForms program that solves it. :cool:

                  That's cool. Mine is just a plain boring console app :->


                  I'd like to help but I am too lazy to Google it for you.

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                  • P Paul Conrad

                    There was a question of if there were more number, yes, there are. Here is a modification of your code that shows others :)

                    #include using namespace std;

                    int main()
                    {
                    int start = 1;
                    int divisor = 10;
                    while ( start <1000000 ) // Or whatevery you want in signed 32-bit range
                    {
                    while (divisor >= 2)
                    {
                    if (start % divisor == divisor - 1)
                    {
                    divisor--;
                    }
                    else
                    {
                    start++;
                    divisor = 10;
                    }
                    }

                        cout<
                    
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                    • P Paul Conrad

                      leppie wrote:

                      So there are more than one of these. I wonder if its some kind of series...

                      Take a look at the modification of Judah's code that I posted. Your number is one of the numbers that come up :)


                      I'd like to help but I am too lazy to Google it for you.

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                      • J Judah Gabriel Himango

                        leppie wrote:

                        I wonder if its some kind of series...

                        It appears to be every 2520.

                        Tech, life, family, faith: Give me a visit. I'm currently blogging about: Messianic Instrumentals (with audio) The apostle Paul, modernly speaking: Epistles of Paul Judah Himango

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                        • R Raj Lal

                          yes thats true there are many , but if you think it might take a day to get the solution , without any computer help, but its worth

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                          • P Paul Conrad

                            Judah Himango wrote:

                            It appears to be every 2520.

                            It is. Modifying the your code that I modified and posted, shows this to be true :)


                            I'd like to help but I am too lazy to Google it for you.

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                            • R Raj Lal

                              Judah Himango wrote:

                              I kind of cheated though

                              well thats ok , and of course there are more numbers but the fun is when you deduce how to do it It's the journey, not the destination

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                              • J Judah Gabriel Himango

                                Provided I've understood the question correctly, I think I've solved it. I kind of cheated though; I wrote a C# program that solves this:

                                        int start = 1;
                                        int divisor = 10;
                                        while (divisor >= 2)
                                        {
                                            if (start % divisor == divisor - 1)
                                            {
                                                divisor--;
                                            }
                                            else
                                            {
                                                start++;
                                                divisor = 10;
                                            }
                                        }
                                

                                Soon as that loop exits, you've got your number, which happens to be 2519.

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                                • J Judah Gabriel Himango

                                  yeah yeah :) Hey, I worked for it at least. :) *edit* oooh, misunderstood you there leppie. I though you were chiding me for solving it with code rather than brain. :) Yes, there are other numbers, it appears every 2520 iteration matches the criteria.

                                  Tech, life, family, faith: Give me a visit. I'm currently blogging about: Messianic Instrumentals (with audio) The apostle Paul, modernly speaking: Epistles of Paul Judah Himango

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                                  • L leppie

                                    Judah Himango wrote:

                                    I kind of cheated.

                                    He did say "find a number" :) So there are more than one of these. I wonder if its some kind of series...

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                                    • L leppie

                                      2701439 last 4 digits by deduction, rest trial and error guess with 3/9 rule. :)

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                                      • A Andrew Bleakley

                                        It's not a mexican is it ?

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                                        • R Raj Lal

                                          Ok lets me be the first to ask a maths question Find a number which 1. divided by 10 gives a remainder 9 2. divided by 9 gives remainder 8 --- --- so on till divided by 2 gives a remainder 1 Any one ?

                                          Omit Needless Words - Strunk, William, Jr.


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