I want to sum all the numbers from B75 to DY75 from worksheet Sheet1 and add that to the sum of all the numbers from B74 to DY74 in worksheet Sheet2 to get my total average. In other words:

```
total average = (sum of the numbers from Sheet1 + sum of all the numbers from Sheet2) / n
```

where n is the total number of numbers.

I've tried `=Average(Sheet1! B75: k74: B74: k74)`

, but that doesn't work.

What formula can I use to accomplish this task?