SOLUTION: Dr. Smith's chemistry midterm has 60 questions. She scores the test as follows: for each correct answer, she gives 2 points; for each incorrect answer, she subtracts 2/3 of a point
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Question 177563: Dr. Smith's chemistry midterm has 60 questions. She scores the test as follows: for each correct answer, she gives 2 points; for each incorrect answer, she subtracts 2/3 of a point; for unanswered questions, she neither gives nor subtracts points. If Andrew scored a 68 and did not answer 2 of the questions, how many questions did he answer correctly? Answer by Mathtut(3670) (Show Source):
You can put this solution on YOUR website! let a,b,and c be the number of correct,incorrect,and unanswered questions, respectively
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a+b+c=60.....eq 1
c=2..........eq 2
2a-(2/3)b=68.eq 3
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lets plug value of c in eq 2 into eq 1
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a+b+2=60--->a+b=58
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a+b=58........revised eq 1
2a-(2/3)b=68..eq 3
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multiply revised eq 1 by -2 and add the two equations together so as to eliminate the a terms. We are left with -2b-(2/3)b=-116+68
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(-8/3)b=-48
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-8b=-144
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: number of correct answers
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