AlgebraMediumCorrect answers from a scoring rule
Algebra practice question
In a quiz of 30 questions, each correct answer scores 4 points and each wrong answer loses 1 point. A student answered every question and scored 85 points. How many questions did the student answer correctly?
Answer: 23
Let c be the number correct: 4c − (30 − c) = 85 → 5c = 115 → c = 23.
Common wrong answers
- If you answered 7
- 7 is the number answered wrongly.
- If you answered 21.25
- 21.25 comes from 4c = 85, ignoring the penalty.
- If you answered 28.75
- 28.75 comes from 4c − 30 = 85, forgetting that fewer wrong answers means a smaller penalty.
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