Saturday, May 9, 2009

5 weights, how to identify them

You have 5 different weights of 1, 2, 3, 4, 5 grams. They are indentical when you observe them. Can you state how many different weighting you need by using a balance which can compare two weights.

1 comment:

  1. 5 weigths can be permuted in 5!=120 ways. There are 3 outcomes when you compare two weigths: left heavier, balance, right heavier. The initial 3^n possibilities can be reduced to one outcome by using n weighting. You have 3^4=81 and 3^5=243. Therefore you need a minimum of 5 weightings