Calculating the average completion across duplicate items

I have a column with a number of duplicate ID’s and a column with percentages, which signifies percentage completion per item i.e. 0%, 25%, 50%, 75% and 100% complete.

I want to work out the average % complete per “unique” item.

I have used the distinct count function in a measure to show only distinct values and added up the percentages for each unique ID. But, now, I think I need to work out how many times each duplicate ID occurs, so, I can use it to divide my rolled up percentages?

I am new to Power BI and any help would be appreciated.