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what is it called ?

Topic closed. 3 replies. Last post 4 years ago by mathhead.

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Posted: September 4, 2012, 5:00 pm - IP Logged

lets say you have the number 93  .  what's it called when you find all the additions that equal 93 ?

 

thank you

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    Posted: September 4, 2012, 5:43 pm - IP Logged

    example   2+5+13+18+22+33 = 93 

    how do you find all the additions  that equal  93 ?

      SergeM's avatar - slow icon.png
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      Posted: September 6, 2012, 1:58 pm - IP Logged

      lets say you have the number 93  .  what's it called when you find all the additions that equal 93 ?

       

      thank you

      It is called wasted time.

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        Posted: September 6, 2012, 8:42 pm - IP Logged

        It is called wasted time.

        Probably a great answer!

        -----

        winrockywin wrote:  ``lets say you have the number 93  .  what's it called when you find all the additions that equal 93 ?``

        I don't know of any particular name.  It is simply as you described:  all combinations of n numbers that sum to x (93).

        Perhaps some lottery "system" (aka "snake oil") has a special name for this kind of "filter" process.  But in that case, SergeM has the "right" answer, IMHO. Wink

        -----

        winrokcywin wrote:  ``example   2+5+13+18+22+33 = 93[.]  how do you find all the additions  that equal  93 ?``

        If you're adept at Excel VBA programming, you can write a macro to generate all possible selections and count the ones that sum to x (93).  You might even write all qualifying sums to the worksheet.

        But you still have not properly explained the problem.  Are you trying to test the sum of all possible subsets of n numbers, that is sums of 2, 3, 4 numbers etc up to n?  Or are you trying to test the sum of, say, any 6 of n numbers?

        And the number of such subsets can be daunting, depending the size of n and the subsets to be summed.

        For example, there are 13,983,816 sums of 6 out of 49 numbers.  And there are 169,339 combinations that sum to 93.

        It took less than 2 sec on my (ancient) computer to generate all of those sums and simply count the qualifying ones.  YMMV.