How to properly find the average percentage of a sum of percentages I’m working with a feature that was broken in several parts, and now my manager wants to know how much is left in each piece and the average percentage as well.
The percentages are 80% + 80% + 50% + 25%
From what I understand I should sum everything and divide by 4, which gives me 58,75%. I would like to know if I’m correct in this assumption or not.
 A: The answer to your question 

I would like to know if I’m correct in this assumption or not.

is maybe, but probably not.
Whether it's correct depends on how the original feature was broken into parts. Suppose there were $100$ subfeatures and the four parts consisted of $40, 40, 8$ and $12$ subfeatures each. Then you would have have left $32 + 32 + 4 + 3 = 71$, so $71\%$ of the original task.
In your example the simple average would be correct if you knew that the four parts were the same size.
You cannot simply average percentages. You need a weighted average where the weights determine how much each of the original percentages contributes to the total.
A: Percentage means over $100$ . So 80 % means 80 over 100 . In other words you got 80 marks from 100. If you sum all of you percentage i.e. $80+80+50+25=235$ so you got 235 from a total 400 . But percentage means over 100 . So  percentage id
$${235 \over 400}.100=58.75%$$
Now all are percentage of a same quantity so you can ignore over 100 since you first divide it and then multiply. And take average directly. 
A: Yes, you're right in your assumption since what you've just done is added four fractions with the same denominator -- which we just do by adding their numerators -- and dividing by $4.$
