# Aptitude - Problems on Trains

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### Overview

• Important Formulas

### Exercise

"Two things are infinite: the universe and human stupidity; and I'm not sure about the universe."
- Albert Einstein
1. km/hr to m/s conversion:

 a km/hr = a x 5 m/s. 18

2. m/s to km/hr conversion:

 a m/s = a x 18 km/hr. 5

3. Formulas for finding Speed, Time and Distance

4. 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.

5. 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.

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) sec. (u + v)

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) sec. (u - v)

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)