To find the part-to-part ratio of the 6th grade averages for the ranges 100-90 and 89-80, we look at the total number of students in each range.
- For the range 100-90, there are 32 students.
- For the range 89-80, there are 65 students.
The part-to-part ratio of the 100-90 range to the 89-80 range is:
\[ 32 : 65 \]
To express this ratio in simplest form, we can divide both numbers by their greatest common divisor (GCD). The GCD of 32 and 65 is 1 (since they have no common divisors other than 1).
Therefore, the simplest form of the ratio remains:
\[ 32 : 65 \]
So, the part-to-part ratio for the 6th grade averages of 100-90 to 89-80 is 32:65.