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Linear and Quadratic Equations · Question 38 of 66

Question 38

MediumOriginal question

A quiz has 40 questions. Each correct answer earns 4 marks and each wrong answer loses 1 mark. Tenzin attempted every question and scored 110. How many did he answer correctly?

Options for question 38

Show the answer and explanation
CorrectNot quiteAnswer C

Correct answer: C

Explanation

  1. Let cc answers be correct; then 40−c40 - c are wrong.

  2. Score: 4c−(40−c)=1104c - (40 - c) = 110, i.e. 5c−40=1105c - 40 = 110.

  3. 5c=1505c = 150, so c=30c = 30.

Worth noting

−(40−c)=−40+c-(40 - c) = -40 + c. Writing it as −40−c-40 - c gives 3c=1503c = 150 and 50, which is more than the 40 questions. 10 is the number of wrong answers.

Concept
Marks with negative marking: a sign trap in the bracket
Typical time
70 s
Your time
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