Isn't there a "RANGE" formula that can be used complimentary with the IF
formula?

I am grading some students' work and am looking to have a IF formula that
divides the students' numeric points earned by the number of possible points
and have the conditions be as follows:

RANGE GRADE
..9-1 A
..8-.89 B
..7-.79 C
..6-.69 D
0-.59 F

What I tried was this:
=IF(C7/C6=RANGE(.9,1),"A",IF(C7/C6=RANGE(.8,.89),"B",IF(C7/C6=RANGE(.7,.79),"C",IF(C7/C6=RANGE(.6,.69),"D","F"))))

However, this did not work because I am either using the RANGE formula
incorrectly or this formula doesn't even exist.

-Zakhary