Two trains starts from place A and B, 450 km apart towards each other. Both trains start simultaneously. A crow sitting on one train start flying at the same time towards the other train and as soon as it reaches the second train, it flies back to the first train and it continues in this manner flying backward and forwards from one train to the other until the train meet. Both train travel  at a speed of 45 km / h and the crow flies at 100 km / h total distance covered by the crow will be 

The Ajmer express can move at 45 km./hr. without its rake and the speed is diminished by a constant that varies as the square root of the number of wagons attached. If it is known that with 9 wagons, the speed is 30 km./hr., what is the greatest number of wagons with which the train can just move?

A train passed by a man standing on the platform in 7 seconds and passed by the platform completely in 28 seconds. If the length of the platform is 330 metres, what is the length of the train?

A train passes two bridges of length 400 m and 200 m. in 50 seconds and 30 seconds respectively. The length of the train is-