There are ten bars all with 1 gram coins except one bar
which contains 2 gram coins....you have a weighing machine ,
which you have to use just 1 time to know which bar has 2 gram coins?

• Take every bar's coin like,
  1st bar's one coin,
  2nd bar's two coin,
  3rd bar's three coin,
  ....
  ....
  up to
  10th bar's ten coin.
  
  Your every bar's coin sum is 55 if there is all 1 gram coin.
  
  In case your sum is become 56 then 56-55=1 it's 1st bar.
  In case your sum is become 57 then 57-55=2 it's 2nd bar.
  In case your sum is become 58 then 58-55=3 it's 3rd bar.
  ....
  ....
  In case your sum is become 65 then 65-55=10 it's 10th bar.
  
• 11 years agoHelpfull: Yes(3) No(0)