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 ? Choose the correct option:  A) 150  B) 155  C) 140  D) 120  E) 165

Rationale: let x be the correct answer and y be the wrong answer so the total number of questions is ( x + y ) = 150 . . . . . ( 1 ) = > 4 x - 2 y = 420 . . . . . ( 2 ) by solving ( 1 ) & ( 2 ) , we get = > 6 x = 720 hence x = 120 therefore , number of correct answers are 120 . answer d
Answer: D