Aptitude - Problems on Trains - Discussion

Distance = time * speed 125 = 10 * speed
distance/time = speed 125/10 = (25/2)m/s = speed
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Answer should be in km/hr so convert m/s
km = 1000m and hr = 3600s
m = km/1000 and s = hr/3600
m/s = (3600/1000)km/hr
m/s = (18/5)km/hr
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The condition was speed = (25/2)m/s
= (25/2)(18/5)km/hr
= 45 km/hr
The speed was relative to man so we have taken time in consideration of man
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See further in in view answer.
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Now I understand that,.

Distance = Speed*Time.

Time = Distance/Speed.

Speed= Distance/Time.

OK guys, very thanks to your teaching.

Can any one tell me why we have mulipled 25/2 to 18/5..why it should not be multiplied by 5/18 and also how ?

x - 5 = 45 ....as I understand it should be 40 km/hr
x = 50 km/hr. Because x=45.

45-5=40....hence anyone pls clarify.

Could anyone please tell me how we get to 25/2 by dividing 125/10. I want to know how the division of 125/10 is done to get 25/2 an answer would be appreciated greatly.

Hi, Really the explanation given by Dattatray & Rahul was superb. Thanks guys.

125/10 = 12.5
3600/1000 = 36/10 (you should delete the last two zeros)
36/10 = 3.6

x = 12.5 * 3.6

So that x = 45 per hour right (this is relative speed of train)

x = 45 (you add 5 km per hour for train speed because 45 is relative speed of train).

Therefore x = 50 (the required answer).

Hai Rahul, well explanation about relative speed and same and opposite directions. Good job keep it up.

@Vijayagopal.

As speed =length/time they have done 125/10. Where 125 is the length and 10 is the time. Hope you understood.

Nice Explanation Guys. Thanks a Lot.

Why 18/5 please tell me?