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Get one half by squaring (Posted on 2004-09-20) Difficulty: 4 of 5
Can you solve the following equation?

= 1/x + 1/y +...+ 1/z

All variables must be different, positive integers, and there must be a finite number of terms.

See The Solution Submitted by Federico Kereki    
Rating: 4.2500 (12 votes)

Comments: ( Back to comment list | You must be logged in to post comments.)
Solution 10 terms... | Comment 22 of 31 |

In answer to David Shin's question, my method was to take out a spreadsheet and let excel calculate the sum and what next variable (integer or not) could finish the job.  I just played around with different variables to see what would work, and my infinite solution seemed to converge on .5.   e.g. seems to have used a similar method, but he obviously did a lot better than I did, because he got a finite solution.  Great job, e.g.

I was very surprised to see that e.g. had found a finite solution, so I had a little more courage and gave the excel spreadsheet another try... this time using a 30 instead of a 25.

I found a 10 term solution within a minute, using the following terms:

2,3,4,5,6,12,30,60,75,100

Hmm, well no wonder we had trouble proving this puzzle impossible.


  Posted by Tristan on 2004-09-21 22:04:06
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