A country gives contract to 8 companies to prepare gold coins. Each gold coin should weigh 10 grams. It was later found that one of the gold coin measured 9 grams. It is known somehow that only one of the company has delivered 9 grams' gold coin. How to find that company by only measuring weight once. Assume that sufficient number of gold coins from each company is available.

• If only one coin is faulty, then it is difficult to find in one weighing.
  
  But if all the coins made by one company are faulty, then it is possible to find that company in one weighing.
  In that case,
  Number the companies as 1,2,3...8
  
  take 1 coin from company 1.
  take 2 coins from company 2.
  take 3 coins from company 3.
  ..
  ..
  take 8 coins from company 8.
  
  weigh these coins.
  In normal case, the weight of 36 coins should be 360 gms.
  
  But as some coins weigh 9 gms, then
  total weight will be less.
  Depending on that , company no can be found.
  
  If weight is less by 1 gm.. company 1 is culprit.
  If weight is less by 2 gm.. company 2 is culprit.
  If weight is less by 3 gm.. company 3 is culprit.
  ...
  If weight is less by 8 gm.. company 8 is culprit.
  
• 13 years agoHelpfull: Yes(12) No(1)