Question

The grades on the last math exam had a mean of 72%. Assume the population of grades on math exams is known to be distributed normally, with a standard deviation of 5%. Approximately what percent of students earn a score between 72% and 87%?

Answer 1

49.9%
1%
50%
47.7%

Answer 2

0.49865 or 49.9

Answer 3

The Z value is 3.
\[\frac{ 87-72 }{ 5 } = 3\]
Look up the probability of Z = 3 at the table you should get 0.99865
Probability at 72 is 0.5
Since you are finding the probability in between 72 and 87:
0.99865-0.5=0.49865