Answer
$7.7$
Work Step by Step
The question asks for the mean growth of the annual rings for the $1920$s.
First, we need to find the total growth of the annual rings for the $1920$s.
Total= $6+8+8+8+8+7+6+6+9+11$
= $77$
Then, we need to divide this total by the number of readings we have, which is 10.
Mean = $\frac{77}{10}$
= $7.7$
