There are 12 coins. One of them is false; it weights differently. It is not known, if the false coin is heavier or lighter than the right coins. How to find the false coin by three weighs on a simple scale?

• Mark coins ABCDEFGHIJKL
  First weighing:-
  
  put ABCD on one side and EFGH on other side of balance.
  
  If equal, then 3rd group, IJKL has the odd coin which can be easily found in next 2 weighings.
  
  If ABCD > EFGH,
  
  it means either one of ABCD is heavier or one of EFGH is lighter.
  
  2nd weighing:-
  Put ABE in one Pan and CDF in other pan.
  
  If equal, one of GH is lighter which can be found in 3rd weighing.
  If ABE>CDF, then either one of AB is heavier or F is lighter which can be found in 3rd weighing by placing A on one side and B on other side.
  
• 11 years agoHelpfull: Yes(7) No(1)