# Number Average Molecular Weight

Example numbers: 2,2,2,2,3,3,3,7,7
```  4(2) + 3(3) + 2(7)     8 + 9 + 14     31
-------------------- = ------------ = ---- = 3.444
4 + 3 + 2              9           9
```
From this it should be obvious that the numbers 2,3, and 7 correspond to "molecular weights" which are represented by the variable M(i), and the numbers 4,3 and 2 correspond to "number average counts", which are represented by the variable N(i).

The symbol i is just an index. For the above data we would have
```M(1)=2, N(1)=4
M(2)=3, N(2)=3
M(3)=7, N(3)=2
```

# Weight Average Molecular Weight

Example numbers: 2,2,2,2,3,3,3,7,7
```      2       2       2
4(2)  + 3(3)  + 2(7)     16 + 27 + 98    141
---------------------- = ------------ = ----- = 4.548
4(2) + 3(3) + 2(7)           31          31
```
It should be clear that M(i) and N(i) are the same as for the Number Average Molecular Weight example.

# Z Average Molecular Weight

Example numbers: 2,2,2,2,3,3,3,7,7
```      3       3       3
4(2)  + 3(3)  + 2(7)      32 + 81 + 686    799
---------------------- = --------------- = --- = 5.666
2       2       2         141          141
4(2)  + 3(3)  + 2(7)
```

Last Update- May 24, 1995- wld