averages: mean of passing scores 78, of failing scores 60,

[allieh]

If 36 students took a test. The mean of those who passed was 78. The mean of those who failed is 60. The mean of all scores is 70. How many students failed the test ?

 

[Denis]

Re: averages

Hint:
f = failed students
78(36 - f) + 60f = ?