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Question
In a competitive examination, there were 60 questions. The correct answer would carry 2 marks, and for incorrect answer 1 mark would be subtracted. Yashwant had attempted all the questions and he got total 90 marks. Then how many questions he got wrong?
Solution
Let the number of correct answers be x and the number of incorrect answers be y.
Total answers = Number of correct + number of incorrect =
x + y = 60 ...(I)
Total marks obtained = 90
2x - y = 90 ...(II)
Adding (I) and (II) we have
x + y = 60
2y − y = 90
+
3x = 150
x = `150/3`
⇒ x = 50
Substituting x = 50 in equation (I)
x + y = 60
50 + y = 60
y = 60 - 50
y = 10
Number of questions he got wrong is 10.
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