I have a txt file that contains some numbers like this: 

```
1  
2  
3  
4  
5  

```

And I have another txt file that contains the same number of lines, but with other numbers:

```
6  
7   
8  
9  
10

```

I want to add them together, namely 1+6, 2+7, 3+8, etc.. How do I write the script?

By the way, I've got a variety of answers so far, and only after I tried them on my files did I realise some of the methods can't deal with decimals. Some of my files contain decimals, and I need to be accurate, so if you would like to add an answer, could you show a method that can calculate decimals accurately. Thanks.