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Question

There are 100 multiple choice questions in an examination.for every correct answer the student gets 5 marks and for every wrong answer 2 marks are deducted from the total score of correct answers.suppose the student attempts all the questions and his total score is 220,how many questions did he attempt correctly?
 


Solution

Let x be correct and y be incorrect  question 
    x+y = total 
    x+y = 100
1 correct = 5 marks 
x correct = 5x 
1 incorrect = 2 marks
y incorrect = 2y marks 
total marks obtained 
 5x-2y = 220 
 x+y =100
   y = 100-x 
5x-2(100-x) =220
5x-200+2x= 220
7x= 420
  x = 60
Number of correct questions attempted = 60 

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