Question

Train m leaves meerut at 5am and reaches delhi at 9am. Another train leaves delhi at 7 am and reaches meerut at 10:30 am. At what time do the trains cross each other?

Answer 1

Lets say, distance between two location be x km. As train departed from meerut at 5 A.M. and takes 4 hours to reach delhi, so we can easily say that it should have covered half of the distance in 2 hours i.e till 7 A.M. .This is the only main part of this question after this only some calucations is left that i’m sharing here.



for train 1; T=D/S => 4=x/s1………………………………………………….equation 1

for train 2; T=D/S => 3.5=x/s2 ……………………………………………….equation 2

After 7 A.M. , we can apply concept of relative speed and distance.

Relative distance will be x/2 and realtive speed will be addition of speed of both the trains as they are moving in opposite direction.

Time = R.D./R.S.

Time = (x/2)/(s1+s2) ……………………………………………………………equation 3

Taking reciprocal of equation 1 and 2 and adding them will gives us

(s1+s2)/x = 15/28
Taking reciprocal of above equation
x/(s1+s2)=28/15 …………………………………………………………………….equation 4

Equating equation 3 and 4,
Time= 14/15 hrs
Time =(14/15)*60 min
Time = 56 min

Answer 2

Thank you for asking this question. Here is your answer:

First of all we will suppose that the trains met at t hrs after 7 am

x is distance between Delhi and Meerut.

Then we will solve it with the following formula:

(x/3.5)*t + (x/4)*(t+2)=x

or  

t/3.5 + (t+2)/4 =1

So, t= 7/7.5 hrs or 56 mins.

Which means that the trains will meet at 7.56 AM

If there is any confusion please leave a comment below.