you have heard of a problem that what minimum number of weights and of what measure you may need if you are asked to measure from 1 to 355Kg each in single weighing.
Note that you can not have more than one weight of a particular measure as if you use then there would be more than one ways to measure certain weights. Thus, it may be regarded as Hint: to measure a particular weight you must have a particular combination of weights.
For the above puzzle the answer is 1,3,9,27,....(log(355)/log(3))Kg.
Now let us apply the same problem to different kind of Libra, are you ready to solve this problem into little different libra