Thread: Calculating a new average from a old average, without knowing the numbers.

I have to calculate a average based on a old average in a voteing system.
but each vote's value have not been stored only the actual vote as count
so what is availible to use is

(exsample)
Old average number : 50
Ammount of votes : 732

And now i want to add new values to that number when there have been
a vote.

Like this

New vote value is between 1-75
a user votes 10.

so im guessing the calculation is something like this

(oldaverage + newvote) / (votecount + 1 new vote)

But it seems off.. any ideas

(732*50 + 10) / 51

Thank you wery much..