Solving the Mystery: Identifying the Faulty Bag of Balls

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    Balls Mystery
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Discussion Overview

The discussion revolves around a problem involving eight bags of balls, where one bag contains heavier balls weighing 2 kg, while the others contain balls weighing 1 kg. Participants explore methods to identify the faulty bag using a weighing machine, emphasizing the challenge of doing so in a single weighing.

Discussion Character

  • Exploratory
  • Mathematical reasoning
  • Debate/contested

Main Points Raised

  • One participant suggests weighing two bags and determining the faulty bag based on whether they balance or not, indicating a simpler approach.
  • Another participant points out that the problem requires a different method since it involves a weighing machine rather than a balance, referencing a similar problem known as the counterfeit coin problem.
  • A different approach is proposed where specific combinations of balls from different bags are weighed to deduce which bag contains the heavier balls based on the total weight.
  • One participant emphasizes the importance of accurately reading the problem statement, highlighting the number of bags involved and correcting a previous claim about the method.
  • A final method is presented where participants are instructed to number the bags and weigh a specific number of balls from each bag, then use the resulting weight to identify the faulty bag.

Areas of Agreement / Disagreement

Participants express differing views on the complexity of the problem and the methods to solve it. There is no consensus on a single approach, with multiple strategies being discussed and some participants correcting each other’s interpretations.

Contextual Notes

Some participants appear to misunderstand the requirements of the problem, leading to confusion about the appropriate methods to use. There are also corrections regarding the arithmetic involved in the proposed solutions.

geniusprahar_21
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try this,
there are eight bags. each bag contains 10 balls. one of those bags contains balls weighing 2 kg(all balls weigh the same). All the other balls weigh 1 kg. you have a weighing machine (not a balance). in one weighing u have to find out which bag contains the faulty balls.
 
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I wouldn't be surprised if there are a lot of threads with problems like this one. This version is far too easy though. Just weigh any two bags. If they balance, then the third bag contains the faulty balls. If they don't balance, the heavier of the two contains them.
 
AKG said:
I wouldn't be surprised if there are a lot of threads with problems like this one. This version is far too easy though. Just weigh any two bags. If they balance, then the third bag contains the faulty balls. If they don't balance, the heavier of the two contains them.

Nope, this is the one where you have a scale - rather than a balance so you weigh a different number of balls from each bag. (This is typically referrred to as the counterfit coin problem.)

Vikasj007 graciously posted a more interesting version which involved 81 bags:
https://www.physicsforums.com/showthread.php?t=33784
 
Oops. He even said "not a balance". Still, this one is too easy. Weigh two balls from bag A together with one ball from bag B. If the total weight is 3kg, then it's bag C, if the weight is 4 kg, then it's bag B, and if it's 5 kg then it's bag A.
 
AKG said:
Oops. He even said "not a balance". Still, this one is too easy. Weigh two balls from bag A together with one ball from bag B. If the total weight is 3kg, then it's bag C, if the weight is 4 kg, then it's bag B, and if it's 5 kg then it's bag A.


How do you keep missing that he said 8 Bags? Its the first line for crying out loud... It still may be easy but at least read what he wrote...

geniusprahar_21 said:
try this,
there are eight bags. each bag contains 10 balls. one of those bags contains balls weighing 2 kg(all balls weigh the same). All the other balls weigh 1 kg. you have a weighing machine (not a balance). in one weighing u have to find out which bag contains the faulty balls.

In white for anyone who doesent know the answer: Number the bags 1-8. Take 1 ball from bag 1, 2 from bag 2, exc.. Weigh the lot of them and subtract 34 from the answer... That is the bag number with the 2kg balls.

EDIT: Thanks Everneo! I did mean 36 :rolleyes:
 
Last edited by a moderator:

did you mean 'subtract 36' ? [/color]
 

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