Arithmatical  Problems on Trains
Important Facts and Formulae
1. 
a km/hr = 

a x 
5 

m/s. 
18 
2. 
a m/s = 

a x 
18 

km/hr. 
5 
3. 
Time taken by a train of length l metres to pass a pole or a standing man or a signal post is equal to the time taken by the train to cover l metres. 
4. 
Time taken by a train of length l metres to pass a stationary object of length b metres is the time taken by the train to cover (l + b) metres. 
5. 
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. 
6. 
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) 