Percentage values based on number of reports not actual percentage value

Hi all,

I'm back again. Todays question is about setting increasing percentage value based on the number of reports finished, not on what the actual numerical percentage. For example, if an employee completes 55 reports, they have achieved 80% of expected production for the day. 56 reports would be 81%, 57 would be 82% up to 75 which is 100%. The problem I am running into is 55 report out of possible 75 is actually 73.33%. The next break point is 65 reports which is 90%, except 65 out of 75 is actually 86.66%. How do I set up the formula to take the number of reports completed and return a percentage value based on an artificial value, not actual math?

I can make a VLOOKUP work if I create a chart with each number and a corresponding percentage value, but I was hoping to use a formula and not have to go with the VLOOKUP option