How can you identify a defective machine with only one use of a scale?

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Discussion Overview

The discussion revolves around a puzzle involving the identification of a defective machine among ten, where one machine produces coins that weigh 10% less than the others. Participants explore the challenge of using a scale only once to determine which machine is defective.

Discussion Character

  • Exploratory, Debate/contested, Conceptual clarification

Main Points Raised

  • One participant expresses uncertainty about solving the puzzle and seeks assistance.
  • Another participant prompts for previous attempts or thoughts on the problem.
  • A hint is provided referencing a mathematical sum, suggesting a potential approach to the solution.
  • A participant mentions a similar problem involving groups of balls with varying weights, sharing a personal anecdote related to memory techniques.

Areas of Agreement / Disagreement

Participants do not appear to reach a consensus on a solution, and multiple viewpoints and approaches are presented without resolution.

Contextual Notes

The discussion includes references to similar problems and personal experiences, which may influence the understanding of the current puzzle. There are no explicit assumptions or definitions clarified.

Who May Find This Useful

Individuals interested in logic puzzles, problem-solving strategies, or mathematical reasoning may find this discussion relevant.

zoich
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I am sure this one has been done a million times, but I can't figure this out. It about 10 mint producing machine and one of them is defective and produces coins that weigh 10% less than the other 9. You have a scale but you can only use it once and only once, how would you identify the defective machine?
 
Mathematics news on Phys.org
What have you tried?
 
Here's a hint: What's 1+2+3?
 
This puzzle has been presented in a slightly different form in the thread entitled: inspector Columbo.
 
I solved another problem of same kind, which says there are 10 groups of 10 balls each and each ball in a group weighs 10gms except one group which has 9 gm balls in it, by an excellent case of coincidence.

When I was in school I had a grave problem with my third language and only way out for me is to mug up. I often used to forget part of the essays and poems, so my teacher advised me to count numbers to calm down myself and try remembering them. I was totally baffled when the above problem was given to me and started counting numbers. I got that when I reached 10.
 

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