Let the length of train ‘A’ be ‘x’ metres Therefore, length of the goods train = ‘5x’ metres Speed of train ‘A’ = 54 × (5/18) = 15 m/s According to the question, 5x + x = 15 × 40 => 6x = 600 => x = 100 Therefore, time taken by train ‘B’ to cross train ‘A’ = {(100 + 200)/(40 + 20)} = 5 seconds