In an examination, a student scored 4 marks for every correct answer and losses 1 mark for every wrong answer. A student attempted all the 200 question and scores 200 marks. Find the number of questions, he answer correctly.
Correct Answer: 80
Explanation:
Let the number of correct answer be x and number of wrong answer be y.
Then, 4x - y = 200 ..(i)
and x + y = 200 ..(ii) On adding Eqs. (i) and (ii), we get
4x - y = 200
x + y = 200
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5x = 400
∴ x = 80
