Submitted by gidon996 on Thu, 01/18/2018 - 18:57
Forums:
In Q4(ii)(b) the answer subtracts 1 from 3^n for the scenario where there are no weights on either scale. However the Q states the inclusion of weighing 0 pounds. Is there a mistake in the answer or am I missing something?
3^n
The answers first start by showing that you cannot weigh more than $3^n$ different weights including 0.
The answers then go on to explain that it is not possible to weigh $3^n$ different weights, this was not asked in the question, but was included in the "solutions" document for interests sake.
So the first line of the "solutions" is actually the answer to Q4(ii)(b), and the rest of the paragraph is an explanation of why you cannot weigh more than $\frac{3^n-1}2$ different, non-zero weights (which you were not asked to do!).