Question 449517
In Professor Tuffguy's mathematics class, 36 students took the final exam. 
Of the average passing grade was 78, the average failing grade was 60, and the class average was 71, 
how many of these 36 students passed the final? 
:
Let x = number of students that passed
then
(36-x) number of students who failed
:
The average equation
:
passed + failed, divided by 36 = 71
{{{(78x + 60(36-x))/36}}} = 71
multiply both sides by 36
78x + 60(36-x) = 36(71)
78x + 2160 - 60x = 2556
78x - 60x = 2556 - 2160
18x = 396
x = {{{396/18}}}
x = 22 students passed