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# 10 must know formulas to solve aptitude problems on trains!

Aptitude problems on trains are one of the most common aptitude problems you’ll come across in competitive exams. To ensure you know how to approach and solve the question as soon as possible, read the following points and remember the formulas given below:

1. km/hr to m/s conversion:
a km/hr = a x (5/18) m/s.

2. m/s to km/hr conversion:
a m/s = a x (18/5) km/hr.

3.  Distance = (Speed x Time)

4. Time taken by a train of length x metres to pass a pole or standing man or a signal post is equal to the time taken by the train to cover x metres.

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

6. 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.

7. 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.

8. 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)/(u + v) seconds

9. 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)/(u – v) seconds

10. 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)

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