There are 80 coins, among them one coin weighs less compared to other. You are given a physical balance to weigh. In how many weighing the odd coin can be found.

• 4 ..divide the 80 coins into 27,27,26. compare the weight of 27 & 27 ...if the weight is same ..the faulty coin is in 26 group of coins...
  in 2nd weighing ....divide the faulty coin group into 9,9,9..again do the same...
  in third weighing divide them into group of 3,3,3
  and in the 4th weighing divide into 1,1,1..
• 13 years agoHelpfull: Yes(15) No(18)
• 80 divide as
  
  27 27 26
  
  9 9 9
  
  3 3 3
  
  1 1 1
  
  so weighings are 4
• 13 years agoHelpfull: Yes(8) No(10)
• first take 40,40 then weight it. which one is less take that 40 coins and now do the same procedure as 20,20. again 10,10 again 5,5.. now in 5 take 2,2,1 first find the weight of 2,2 if these are equal then remaining last one is the less weight coin. otherwise Again consider 2 coins in which we can find out The Less Weight..
  So, finally 5 or 6 steps needed to find out the Answer.......
• 11 years agoHelpfull: Yes(8) No(5)
• divide coins into 3 groups,27,27,26.
  1st weighing : first compare the weight of 27 and 27.If
  they are equal then the third collection of 28 coins
  contains the faulty coin else the lesser weighing collection
  of 27 coins has the faulty coin.
  2nd weighing : then divide the 27 coins into 9,9,9 of three
  groups ,again compare the two 9's of them.if they are equal
  then the third collection of 9 coins contains the faulty
  coin else the lesser weighing collection of 9 coins has the
  faulty coin.
  3rd weighing : then divide the coin in 3 groups of 3.again
  compare the two 3's of them.if they are equal then the third
  collection of 3 coins contains the faulty coin else the
  lesser weighing collection of 3 coins has the faulty coin.
  4th weighing :now compare the two coins of them.if they are
  equal then the third coin is the faulty coin else the lesser
  weighing coin is the faulty coin
• 8 years agoHelpfull: Yes(3) No(0)