Answer:
98
Step-by-step explanation:
You want to know the score that will result in an average of 90 if four of the five scores are 78, 92, 83, 99.
For the average score to be 90, the total difference of scores from average must be zero. When 90 is subtracted from the given scores, we get ...
-12, +2, -7, +9
for a total of -8, which is 8 points less than needed.
To bring the average to 90, Ramesh must score 8 points more than 90 on the 5th test.
Ramest needs a score of 98.
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Additional comment
We find it convenient to work the problem this way because it can be done entirely with mental arithmetic. The usual method would be to add the given scores, then find the difference of that sum from the value of 5 times the desired average.
