Car seat belts are tested for strength, and it is found the results are normally distributed with a mean of 2400 lb and a standard deviation of 400 lb. Using the 68-95-99.7 rule, find the percentage of scores between 1600 lb and 3200 lb.

Answer 1

95.45 %
see:
http://davidmlane.com/hyperstat/z_table.html

I have no idea what the rule is.