he grades of a group of 1000 students in an exam are normally distributed with a mean of 70 and a

  • The grades of a group of 1000 students in an exam are normally distributed with a mean of 70 and a standard deviation of 10. A student from this group is selected randomly.
    a) Find the probability that his/her grade is greater than 80.
    b) Find the probability that his/her grade is less than 50.
    c) Find the probability that his/her grade is between 50 and 80.
    d) Approximately, how many students have grades greater than 80?