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
