In a quiz every correct answer scores 5 marks and every wrong answer loses 2 marks. Anil attempted all 20 questions and finished with 65 marks. How many did he get right?

Question

Accepted Answer

15. Let c be the correct answers; the wrong ones number 20 − c. So 5c − 2(20 − c) = 65 → 5c − 40 + 2c = 65 → 7c = 105 → c = 15. Check: 15 right = 75 marks, 5 wrong = −10 marks, total 65 ✓. Answer 13 ignores the penalty; 21 forgets to distribute the −2 across the c (5c − 40 = 65); 35 flips the sign inside the bracket — and 35 correct out of 20 questions should have warned you at once.

In a quiz every correct answer scores 5 marks and every wrong answer loses 2 marks. Anil attempted all 20 questions and finished with 65 marks. How many did he get right?

Step-by-Step Solution

Key idea: Translating word problems into equations

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