An express train takes 2 hours less time than a passenger train to travel 400 km between two stations (without taking into consideration the time they stop at intermediate stations). If the average speed of the express train is 10 km/h more than that of the passenger train, find the average speed of the train.

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answer is B.

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Detailed Solution

Concept- As we can see in the question the Time , distance are given and we need to find the speed.
Do it we can use the relation between these three that is

Let’s assume that the average speed of train is

km/hr and the average speed of passenger speed is

km/hr.
As per the relation

As per given question the distance covered by both trains is 400km , so now let take

hour and

hour.

As per the question the difference between the time is 2 .
Question Image

As per the given question express train speed is

km/h by passenger train.
So, now

Let’s use equation (i) and (ii)
We will put the value of

from eq(i) in eq(ii)
Question Image

Now to solve this equation we will use the quadratic equation as equation is given in

where

Now we will find the value of y using the above the formula
Question Image

Now we got two values of y
Question Image

As we know that speed cannot be negative, so the speed is 40km/hr.
Hence, the correct answer is option 2.

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