Problems on Trains on Arithmetic Aptitude related Questions and Answers

Question :   A train running at certain speed crosses a stationary engine in 20 seconds. To find out the speed of the train, which of the following information is necessary: 1. Only the length of the train 2. Only the length of the engine 3. Either the length of the train or the length of the engine 4. Both the length of the train and the length of the engine Answer :   4 - Both the length of the train and the length of the engine