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.

• A. 36
• B. 18
• C. 9
• D. 27

Answer 1

Answer: (C)

9

Answer 2

Let's take the number of correct answers be C and the number of wrong answers be W.
C + W = 90 — Equation(1)
5C - 2W = 387 —Equation(2)
After Multiplying equation 1 by 5 and then subtracting it from Equation 2, we get
7W = 450 - 387 = 63
W = $\frac{63}{7}$
W = 9
The correct option is (C)