SOLUTION: if 35 students average 80% and 15 average 70% what is the total average of all 50 students?

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Question 772436: if 35 students average 80% and 15 average 70% what is the total average of all 50 students?
Found 2 solutions by solver91311, josmiceli:
Answer by solver91311(24713) About Me  (Show Source):
You can put this solution on YOUR website!


The sum of the scores of the first 35 students is 35 times 80. The sum of the scores of the scores of the other 15 students is 15 times 70. The sum of the scores of all 50 students is the sum of your first two calculations. The average is that grand total divided by 50.

John

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Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
The lesson here is that you can't get an average
by taking the average of 2 averages. You must
use the formula:
Average = ( sum of all the scores ) / ( total number of students )
--------------------------
Use the formula:
Average = ( sum of scores ) / ( number of students )
Sum of scores = ( Average )*( number of students )
-------------------------------------------
1st sum of scores =
+.8%2A35++=+28+
2nd sum of scores:
+.7%2A15+=+10.5+
----------------
Number of students is +35+%2B+15+=+50+
----------------
Average = ( sum of all the scores ) / ( total number of students )
Average = +%28+28+%2B+10.5+%29+%2F+50+
Average = +38.5%2F50+=+.77+
The average for the 50 students is 77%