My name is Rachel
I am in 9th grade Honors Geometry

My question is - In Mr. Edgecomb's math class, 30 students took an exam on statistics. If the average passing grade was 84, the average failing grade was 60, and the overall average was 80, how many students passed the test?

I have no idea how to start this problem. I have to show my algebraic work. I would appreciate help getting started on this problem. Thank you in advance for your help.

Hi Rachel.

When Mr. Edgecomb calculated the average for all 30 students he added their scores, dived by 30 and got 80. Thus the total of all the scores was 30x80 =2400.

Suppose than n students passed the exam and the total of their scores was T, then T/n = 84. Since n students passed the exam, 30 - n students failed the exam. The total of their scores was 2400 - T and hence their average was (2400 - T)/(30 - n) = 60.

Can you finish the problem now?

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