mymy28
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A professor has recorded exam grades for 20 students in his class, but one of the grades is no longer readable. If the mean score on the exam was 81 and the mean of the 19 readable scores is 85, what is the value of the unreadable score?

Respuesta :

texaschic101
20 students....mean score of exam was 81...

x / 20 = 81
x = 81 * 20
x = 1620....this is the total of all the grades added up

(1620 - x) / 19 = 85
1620 - x = 85 * 19
1620 - x = 1615
-x = 1615 - 1620
-x = - 5
x = 5 <=== weird answer...but thats what I am getting

The value of the unreadable score is [tex]5[/tex]

It should be noted that the mean of numbers simply means the average of the numbers.

Since the mean score of the 20 students was 81, then the total score will be: [tex]= 20 * 81= 1620[/tex]

Then, since the mean score of the 19 students was 85, their total scores will be: = [tex]19 * 85 = 1615[/tex]

The value of the unreadable score will be:

[tex]= 1620 - 1615 = 5[/tex].

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