# Sum and then divide columns

So I have a list in which a column needs to be summed up, then grouped so I can create another column that allows me to do division off of the summed total. So for instance

John Doe 1 - 0 - 1
John Doe 1 - 1 - 0
John Doe 1 - 1 - 1
John Doe 1 - 1 - 1
John Doe 1 - 1 - 0

John Doe 5 - 4 - 3 Summarized Calculation 5-3/4

Problem is that we cannot do the calculation by line because you can't divide a number by zero as the second first line is. But we can do the calculation based off of the sum.

I looked at the documentation using a workflow to do this, however a line may be deleted and then how do you reconfigure the totals in a new list, and do this in live time.

Anyone have any thoughts on this?