Quants - Train Shortcuts

• Time taken by a Train of length l meters to pass a pole or a standing man or a signal post is equal to the time taken by the Train to cover l meters.
• Time taken by a train of length l meters to pass a stationary object of length x meters is the time taken by the train to cover (l+x) meters.
• Suppose the trains or two bodies are moving in the same direction at u m/s and v m/s, where u > v, then their relatives speed = (u-v) m/s.
• Suppose two trains or two bodies are moving in opposite directions at u m/s and v m/s, then their relative speed is = (u+v) m/s.
• If two trains of length x meters and y meters are moving in opposite directions at u m/s and v m/s, then time taken by the trains to cross each other = (x+y)/(u+v) sec.
• If two trains of length x and y meters are moving in the same direction at u m/s and v m/s, then the time taken by the faster train to cross the slower train =  (a+b)/(u-v) sec.
• If two trains or two bodies start at the same time from points P and Q towards each other and after crossing they take x and y sec in reaching Q and P respectively, then (Speed of P):(Speed of Q) = (SQRTy : SQRTx).
• x km/hr = (5x/18)m/s.
• x m/sec = (18x/5)km/hr.