The 12 Ball Problem LO9606

Walter Derzko (
Thu, 29 Aug 1996 21:34:11 -0400

I'm giving the following 12 Ball Problem to my Conestoga College students
next week. It's a warm up team-building exercise that I do in the first week
in a course on learning strategies and a course on thinking skills in business.

I think it would make a good exercise in most training and development

The goal is not just to come up with one or more solution strategies but
to explore and document your thinking on developing strategies that did and
didn't work. Did your thinking proceeded to a solution or to a cognitive
roadblock or dead end ?

I was told that this was an unsolvable problem but I came up with one
solution strategy after about 15 minutes of doodling and three wrong starts.
This one solution strategy lead to three ways of solving the problem.

I suspect that there may be more.

One hint - the solution came to me after an insight change.

So here goes...
The 12 Ball Problem

There are twelve balls, identical in appearance, but one is either
heavier or lighter than all the others. Using only a balance scale (ie two
balanced pans and no weights) and using it only three times, isolate the
odd ball and be able to say in which way it differs. Is it heavier or
lighter than the rest ?

I'd like to know your sequence of thinking. I'm looking for both wrong and
right thinking strategies. ( I give students marks for both)


I found it easy to isolate the odd ball in three steps but you
couldn't tell if it was heavier or lighter. (This partial solution does
not meet the requirements. Just as in the real world, half done is not


1) How did you start and what was the sequence of your thinking ?

2) What roadblocks in thinking or what problem-solving obstacles did you
experience ?

3) If you came up with a correct solution strategy, what was the insight
change ?

Email me your thinking sequences (right or wrong) and I'll post a summary
of the novel ones.

My email is

Good luck !

[Host note: Please respond by email to Walter, and Walter, please summarize
the results for us. I suspect the results you get will be of great interest
to the group. Johanna, temporary LO host,]

Walter Derzko
Founder Creativity Consortium
An international club/network for lateral thinkers (until May) (after)
(416) 588-1122


Walter Derzko <>

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