posted by preston .
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?
Since the mean score of the 42 students was 75.5, the sum of all the scores of all students was 75.5(42)
let the number of students who passed be x
then 42-x must have failed
the sum of the scores of the passing students is then 81x, and
the sum of the scores of the failing students was (42-x)(60)
so isn't 81x + (42-x)(60) = (42)(75.5) ???
Take it from there