08 Oct '15 13:34

I'm sure many of you have heard of the 12-weight problem. There is a version of it on the wikipedia page:

https://en.wikipedia.org/wiki/Balance_puzzle

My problem is similar but only involves 9 weights. You have 9 identical looking weights all of which are the same weight except 2, one of them is slightly lighter than the rest and the other one is slightly heavier than the rest by the same amount. In other words 7 of them weigh x grams, one of them weighs x-e grams and the other one x+e grams.

How can you determine which weight is the heavier one and which is the lighter one in just 4 weighing on a set of balance scales?

https://en.wikipedia.org/wiki/Balance_puzzle

My problem is similar but only involves 9 weights. You have 9 identical looking weights all of which are the same weight except 2, one of them is slightly lighter than the rest and the other one is slightly heavier than the rest by the same amount. In other words 7 of them weigh x grams, one of them weighs x-e grams and the other one x+e grams.

How can you determine which weight is the heavier one and which is the lighter one in just 4 weighing on a set of balance scales?