SOLUTION: Please help me solve this: Marcus tried to compute the average of his 8 test scores. He mistakenly divided the correct total S of his score by 7. The result was 12 more than what

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Question 588782: Please help me solve this:
Marcus tried to compute the average of his 8 test scores. He mistakenly divided the correct total S of his score by 7. The result was 12 more than what it should have been. Which equation would determine the value of S?
A. 8S-12=7S
B. S/7=S+12/18
C. S/7+12=S/8
D. S/7-12=S/8

Answer by jim_thompson5910(35256)   (Show Source): You can put this solution on YOUR website!
"He mistakenly divided the correct total S of his score by 7", so we know that S/7 is in there somewhere.


The true average is really S/8.


Since the mistaken result (S/7) is 12 more than what it should have been (S/8), this means that

S/7 = S/8 + 12


Now subtract 12 from both sides to get the final answer

S/7 -12 = S/8

which is choice D.
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