Profit in percentage

• A shopkeeper bought a watch for Rs.400 and sold it for Rs.500.What is his profit percentage?
  
  For the Answer of this puzzle read my next POST......
  
  
• Answer of Puzzle : 6
  
  If A, B and C are the mechanisms used separately to reduce the wastage of fuel by 30%, 20% and 10%. What will be the fuel economy if they were used combined ?
  
  Answer is:
  
  20%