This ain't really a school question, but there doesnt seem to be a no-school one 
Anyways, I want to keep track of my cars fuel usage, so I made am Excel sheet where I track odometer count, fuel charged and (irrelevant) the price.
Now this worked fine until now with the formula fuel/km*100 but I now encountered and issue.
At the kast fuel station, I could only charge preset amounts, so I didnt fill the whole tank as I used to. This now gives me a low usage for that tank and a big one for the following one.
Is there any way to get around this and calculate the inbetween step? Or will I have to basically sum the fueling + the next full one together?