Exercise :: Problems on Trains  Important Formulas
 Problems on Trains  Important Formulas
 Problems on Trains  General Questions
 Problems on Trains  Data Sufficiency 1
 Problems on Trains  Data Sufficiency 2
 Problems on Trains  Data Sufficiency 3

km/hr to m/s conversion:
a km/hr = a x 5 m/s. 18 
m/s to km/hr conversion:
a m/s = a x 18 km/hr. 5 
Time taken by a train of length l metres to pass a pole or standing man or a signal post is equal to the time taken by the train to cover l metres.

Time taken by a train of length l metres to pass a stationery object of length b metres is the time taken by the train to cover (l + b) metres.

Suppose two trains or two objects bodies are moving in the same direction at u m/s and v m/s, where u > v, then their relative speed is = (u  v) m/s.

Suppose two trains or two objects 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 a metres and b metres are moving in opposite directions at u m/s and v m/s, then:
The time taken by the trains to cross each other = (a + b) sec. (u + v) 
If two trains of length a metres and b metres 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) sec. (u  v) 
If two trains (or bodies) start at the same time from points A and B towards each other and after crossing they take a and b sec in reaching B and A respectively, then:
(A's speed) : (B's speed) = (b : a)