Mr. Johnson gave his class an exam the day before Christmas break. The average score for all students was 80. The average score for those who passed was 84 and for those who failed was 60. If there are 60 students in the class, how many failed the exam? Can anyone explain how to set this up?Thanks to all those whose answers are helpful ^_^
2007-01-27 00:57:58 · 3 answers · asked by msdrosi 3 in Education & Reference ➔ Other - Education
You need to look primarily at the *total score*.
Say A students passed and B failed.
So you have (A x 84) + (B x 60) = 4800.
In addition, you also know A + B = 60.
You get a simultaneous equation, which you need to solve by standard methods.
It's easy. Since A = 60 - B, you have
84(60 - B) + 60B = 4800
So 5040 - 84B + 60B = 4800
So 24B = 240
So B = 10. 10 Students Failed.
2007-01-27 01:06:41 · answer #1 · answered by Anonymous · 1⤊ 0⤋
Total marks scored by class
60 students x 80 marks(average) =4800 marks
Students who failed (F) + students who passed(P) = 60
P= 60 - F
total marks by average score --(P x 84) + (F x 60) =4800
So.... by substituting P with 60-f...
((60-f) x 84) + (F x 60) =4800
5040 -84F + 60F = 4800
24F= 240
F=10
10 students failed the exam.....
2007-01-27 09:19:53 · answer #2 · answered by Geinius 3 · 1⤊ 0⤋
80*60= 4800, the total sum of all the marks in the class. 10 students failed the exam! 60 *10=600, 4800-600= 4200, if you divide 4200 by 50 you get 84, the average passing mark.
2007-01-27 09:12:18 · answer #3 · answered by rennieboy 1 · 1⤊ 0⤋