math
posted by devon on .
A class of 43 students took an exam. Their mean grade average is 67 and standard deviation is 7.
a) how many students should get a C?
b) how many should get a B?
c) what score is necessary to get an A?

Here is an excellent applet that will do these kind of questions.
http://davidmlane.com/hyperstat/z_table.html
Unless I know what is considered a C in your country or region, I can't finish the problem for you
enter the mean, the standard deviation, then choose the "between" option
Enter the low end and the high end of your letter grade range. 
(pushed the post button too early)
the result you get will be a decimal between 0 and 1, the probability.
multiply that by the number of students, the 43