math
posted by preston on .
42 students took a test in school where the passing score was 70. the mean score of the 42 students taking the exam was 75.5 while the mean score of the students who passed the test was 81, and the mean score of the students who failed was 60. How many students passed the test?

The mean above 70 is 81, the mean of the students below is 60.
Let nf be the number of students that failed.
sumfaildgrades+sumpassedgrades=total sum grades.
nf*60+(42nf)81=42(75.5)
check that. solve for nf.