Help hiding cell value prior to info input

Hey guys, I have scoured endlessly to try and figure this out on my own, but nothing is working yet and it's driving me crazy. I'm trying to make a list with 9 questions with a "Yes, No, or Partial" answer with a 100, 50, or 0 attached to each answer, then at the end of the list, take the total sum of the points/answers and divide them by the amount of questions asked so that I can find the average, then assign a grade letter based on the number results. So far so good, my only problem is that before I start and begin answering any questions, the letter "A" shows up instead of just a blank cell like I want, at least until one or more questions have been answered.

This is my formula I'm using, and the grading is working properly, just not the show blank cell if nothing is answered yet part.

=IF(D27>=90,"A",IF(D27>=80,"B",IF(D27>=70,"C",IF(D27>=60,"D",IF(D27>=10,"F",IF(D27<=1,""))))))

;the red coding is what I made to attempt to hide a value below 10, but it's not working and still shows an "A" grade before any questions have been answered.

Screenshot of the project for reference
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I very much appreciate any help anyone can offer with this issue. It's really not a major problem, I would just really like to figure it out. You'd think something like this would be incredibly simple to figure out.