In a classroom test, students were awarded +6 marks for each correct answer and –3 marks for each incorrect answer. No marks were given for unattempted questions. Radhika answered 10 questions correctly and scored a total of 42 marks. How many questions did she answer incorrectly?
6
Let the number of incorrect answers be x. Total score = 6 × (correct answers) – 3 × (incorrect answers).
Substitution: \(6 \times 10 - 3x = 42\).
Working: \(60 - 3x = 42 \Rightarrow 3x = 18 \Rightarrow x = 6\).
Check: marks for correct answers = 60, deduction = \(3 \times 6 = 18\), and 60 – 18 = 42, which matches the total score.
Hence, 6.
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