Find 10 items out of 100+ adding up a certain sum

[halixol]

Hi ,

I have 100+ numbers (3.4, 332.4, 24.12, etc) on my report.
I also have a subtotal (eg. 1234.56) from a separate source.
I know that 10 items out my long report add up this subtotal, but do not know which.
The Question: Can Excel tell me any way which are those 10 numbers that add up the subtotal?
I know that theoretically there can be many combinations, especially if some numbers duplicate, however in practice this does not happen too often.
Thank you.

 

[RalphA]

Is this homework? I seem to see this type of question every now and then:

"I have n numbers. I also have a given total. Can Excel tell me what combination of m numbers will add up to the given total?"

Surely, if this problem is a dooable one, there must be more than one answer already submitted, and one should be able to find it.

My opinion? For the combination of 100 things taken 10 at a time, Excel's formula: =COMBIN(100,10) gives 17,410,000,000,000. As can be easily imagined, to run a program that tests, on average, half of this number to come up with the various ones whose sum equals the given total may take longer than I have time to wait! So, it may be there is a solution, but, it is not practical.

If I am wrong, I would relish seeing the program that can find the answer(s) in less than, say, 10 minutes. That is, on our normal 3 GHz or so computers, with no more than some 500 MBytes of memory.

 

[halixol]

This is no homework at all , but a problem occuring at least once per week at my workplace. Actually i need to know which are those numbers, and not how many combinations Excel needed to go through ( i believe this your quoted example question about)

Does anyone has a working solution to this problem, and does it really take so much time?

 

[PaddyD]

one approach:

http://www.mrexcel.com/board2/viewtopic.php?t=23107

...but make sure to follow the link for the full discussion, which indicates why the problem is somewhat intractable...

 

[halixol]

This is indeed the solution i required.
Thank you for the quick help.