In an objective competitive exam, a correct answer score 4 marks and on a wrong answer 2 marks are negatively added. A student scores 420 marks from 150 question. How many answers were correct ?
Correct Answer: 120
Explanation:
let x be the correct answer and y be the wrong answer
so the total number of questions is (x + y) = 150.....(1)
=> 4x - 2y = 420.....(2)
By solving (1) & (2), we get
=> 6x = 720
hence x = 120
Therefore, number of correct answers are 120.
