Answer:



And in the figure attached we see the limits with the percentages associated.
Step-by-step explanation:
For this case we know that the random variable of interest is the scores on a test given to all juniors in a school district follows a normal distribution with the following parameters:

For this case we know from the empirical rule that within one deviation from the mean we have approximately 68.2% of the data, within 2 deviations from the mean we have 95% and within 3 deviation 99.7%
We can find the limits and we got:



And in the figure attached we see the limits with the percentages associated.
(8.5*12.4)^(1/2)=10.266
In general the geometric mean is (ab)^(1/2), (abc)^(1/3), (abcd)^(1/4), etc
The nth root of the product of n elements.
13. 81.64
14. 803.84
15. 153.83
16. 753.6
you just use circumference and area formulas for a circle
The probability will be 3/6 or 1/2