Divide 40 kg mass into 4 piece such that you can weigh from 1 to 40 kg from those 4 masses

  I assume you mean an whole number weight from 1 to 40 kg. 

 
27 kg 
9 kg 
3 kg 
1 kg 

To weigh 1 kg, that's obvious. 
To weigh 2 kg, put 3 kg on one side, 1 kg on the other. Put your object with the 1 kg weight and make it balance. 
To weigh 3 kg, that's obvious 
To weigh 4 kg --> 3 kg + 1 kg 
To weigh 5 kg --> 9 kg on one side, 3 kg + 1 kg on the other 
To weigh 6 kg --> 9 kg vs. 3 kg. 
To weigh 7 kg --> 9+1 kg. vs. 3 kg. 
To weigh 8 kg --> 9 vs. 1 
9 --> 9 
10 --> 9 + 1 
11 --> 9 + 3 | 1 
12 --> 9 + 3 
13 --> 9 + 3 + 1 
14 --> 27 | 9 + 3 + 1 
15 --> 27 | 9 + 3 
etc. 

You should be able to follow the pattern all the way to 40 kg.
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