In an examination, a student scores 4 marks for every correct answer and losses 1 mark for every wrong answer. A student attempted all 200 questions and scored 500 marks. What is the number of questions, he answered correctly?
140
The correct answer is 140.
Using Substitution: Start with Equation 1: c + w = 200 Solve Equation 1 for w : w = 200 - c Substitute this expression for w into Equation 2: 4c - (200 - c) = 500 Simplify and solve for c : 4c - 200 + c = 500 \implies 5c - 200 = 500 \implies 5c = 700 \implies c = 140 Both methods give the same result for the number of correct answers, which is 140.
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