Answer :
Answer:
B. 96
Step-by-step explanation:
Let x represent score of final third exam.
We have been given that in a given course a student receives preliminary examination grades of 81, 85, and 95.
Let us find average of preliminary scores.
[tex]\frac{81+85+95}{3}=\frac{261}{3}=87[/tex]
We have been given that the final examination is weighed for one-third and the average of the preliminary grades is weighed as 2/3 of the final grade. This means that final grade is equally weighed into 3 parts. The two parts are 87 each and third part is x.
Using our given information, we can set an equation as:
[tex]\frac{87+87+x}{3}=90[/tex]
[tex]\frac{174+x}{3}=90[/tex]
[tex]\frac{174+x}{3}*3=90*3[/tex]
[tex]174+x=270[/tex]
[tex]174-174+x=270-174[/tex]
[tex]x=96[/tex]
Therefore, the final examination grade should be 96 for a semester average of 90.