Question

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?
The value of the unreadable score is
nothing.

Answer 1

Answer:

5

Step-by-step explanation:

To obtain the total score for all the 20 students, we multiply the average score by the number hence

Total score for all 20 is 81*20=1620

Similarly, for the 19 students, the sum of their total score equals the product of the average and number of students hence

Total score for 19 readable is 19*85=1615

The difference between these two total scores ie for 20 and 19 students equals to the value of unreadable score. Therefore,

Difference=1620-1615=5

Therefore, the value of unreadable score is 5