Posted by liz on .
A prof. teaches 2 calc. classes. The first class has 25 students and their mean on the 1st test was an 82. The 2nd class has 15 students and their mean on the same test was a 74. What is the mean on this test if the prof. combines the score for both classes?
Is the answer the mean cannot be calculated since the individual scores of each student are not available.

Math for the middle school and elementary teacher 
MathMate,
To calculate the mean, you need the total score and the total number of students.
Can you find a way to reconstitute these two numbers, knowing that
mean = total score / number of students 
Math for the middle school and elementary teacher 
liz,
I don't think you can find the total score because you would need the individual scores, right? I tried dividing 82/25 but that wouldn't work because we don't have all the scores...am I on the right track if not, can i please have some guidance? thank you!

Math for the middle school and elementary teacher 
MathMate,
hint:
For each class
mean = total score / number of students
=>
for each class
total score=mean*number of students
So the total score for each class is known. Can you find the total score for both classes? Total number of students? 
Math for the middle school and elementary teacher 
liz,
The answer is 79, correct? Thank you for your guidance and help:)

Math for the middle school and elementary teacher 
MathMate,
Excellent & well done!! :)