Shortcut Trick for Problems based on Trains Questions

problems based trains

First we need to know how to convert kmph to mps :

Example : Convert 72 kmph to mps ?

In traditional method we need to multiply 5/18 to 72

⇒ 72
×5/18 = 20 mps

Here its seems to be easy but in problems speed is in fractions we face difficult.


Tricky method :

Here what ever the speed given in problem(fractions also) we just multiply with 10 , the resultant is how many meters it travel in 36sec , from this we can easily find out " mps"

Example : Convert 14.4 kmph to "mps" ?

Multiply kmph with 10,it gives how many meters it travelled in 36 sec

14.4 × 10 =144

⇒ 144  --------- 36

⇒  ?       ---------- 1

From this cross multiplication we need to find 1 mps

 144/36=4 mps

How to Convert Mps To Kmph ? :

Similarly we need to know " how to convert "mps" to "kmph" 

Example : Convert 4 mps to kmph ?

Here we need find out first how many meters it travelled in 36 sec

?  ------  36
4  ------  1

= 144 

Here we need divide with 10

= 144/10 = 14.4 kmph

Examples :

Ques 1.

A train is 100 meter long and is running at the speed of 30 km per hour. Find the time it will take to pass a man standing at a crossing.?
Answer :   

30×10 ------ 36
100.   ------   ?
= (36×100)/(30×10) =12 sec

Ques 2.

A train is moving at a speed of 132 km/hour. If the length of the train is 110 meters, how long will it take to cross a railway platform 165 meters long.
Answer :

Total length need to cross train is 110+165= 275m
132×10  ------- 36
275        -------   ?
= (36×275)/(132×10) = 7.5 sec

Ques 3.

Speed of a goods train is 72 km/hr. This train crosses a 250 meter platform in 26 seconds. Then find the length of goods train.
Answer :
Platform length =250m

Here take " x " as train length total length train need to cross = ( x + 250)m

(72×10)  ------ 36
(X+250) ----- 26

  36×(x+250) = (72×10)×26
  x =270 m

Ques 4.

A train speeds past a pole in 15 seconds and a platform 100 meter long in 25 seconds. What is length of the train ?
Answer :
Take train length as " x "
Total length its need to cross in 26sec is = (26+x)
  
X ------- 15
(100+x)-----25

⇒ 25x = 1500+15x
 10x = 1500
 x = 150m

Ques 5.

Two trains of equal length are running on parallel lines in the same direction at 46 km/hr and 36 km/hr. The faster train passes the slower train in 36 seconds. The length of each train is
Answer :
here train lengths are equal 

⇒ Take it as "x" , so faster train need to cross total length of two trains = x+x= 2x faster train crosses slower train in 36sec

⇒ Trains are traveling in same direction , so relative speed is = 46 - 36 = 10kmph

⇒ 10×10 ------36
⇒ 2x       -------36
    2X =100
⇒ x =50m

Note: By this method we can easily calculate without pen and paper .

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