Question

in an objective examination of 90 questions, 5 marks are allotted for every correct answer and 2 marks are deducted for every wrong answer. after attempting all the 90 questions, a student got a total of 387 marks. find the number of questions that he attempted wrong.

Answer 1

let number of correct answered question = x

let number of  wronged answered question = y

x + y = 90       [ all 90 questions were attempted ]

x = 90 - y     ----------------------------- eq1

marks from correct question = 5x

marks from wrong question = -2y   [ used negative sign as wrong marks are deducted]

5x - 2y = 387   ------------------------------eq2

substituting value of x from eq 1 in eq 2

5(90 -y)  - 2y = 387

⇒450 - 5y - 2y = 387

⇒ -7y = 387 - 450

⇒ -7y = -63

⇒  y = -63/(-7) = 9

hence 9 questions are wrongly attempted

⇒

Answer 2

Step-by-step explanation:

Answer is 9

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