Aptitude

problem on trains

Important Formulas

1. m/s to km/hr conversion:

   a m/s =		a x	18		km/hr.
   			5

2. km/hr to m/s conversion:

   a km/hr =		a x	5		m/s.
   			18

   
   

3. 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.

4.  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.

5.  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.

6.  two trains of length a metres and b metres are moving in opposite directions at u m/s and v m/s .

   The time taken by the trains to cross each other =	(a + b)	sec.
   	(u + v)

7.  two trains of length a metres and b metres are moving in the same direction at u m/s and v m/s, then their relative speed is = (u - v) m/s.

8.  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.

9.  two trains of length a metres and b metres are moving in the same direction at u m/s and v m/s, 

   The time taken by the faster train to cross the slower train =	(a+b)	sec.
   	(u - v)

10.  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, 

    (A's speed) : (B's speed) = (b : a)