pudipeddi wrote:

Anjalika123 wrote:

galiya wrote:

A passenger sitting near the window in a train moving at 40 km/h, noticed that it took 3 sec. for the oncoming train to pass by. What was the speed of the oncoming train if the length of the oncoming train was 75 metres?

a)50km/h

b)52km/h

c)56km/h

d)60km/h

e)70km/h

let

x is speed of the oncoming train

sum of speed of both the trains * time taken=length that both the trains covered

(40+x)3/(3600)=75/1000+40*3/(3600)

after solving :

x=90 km/h

I don't know where I went wrong.

Plz someone tell where I went wrong and share the solution.

You should be considering the length of the train that is passing as the point of reference is you. Hence distance covered is 75 meters only.. Not the length of the train in which you are sitting

Posted from my mobile device pudipeddiThe distance travelled by the train in which the passenger sat will also be taken into

consideration because the train is not stationary but moving at a speed of 40kmph

So, the train will also travel some distance in those 3 seconds.

If the incoming train travels at a speed of 40 km/hr, it would translate into \(\frac{100}{9}\) m/s.

In 3 seconds, the train would have travelled \(\frac{100}{3}\) meters.

The total distance travelled in 3 seconds would be \(75 - \frac{100}{3} = \frac{125}{3}\) meters in 3 seconds.

The distance(125/9 m/s) translated in km/hr is \(\frac{125}{9}*\frac{18}{5}= 50\)kmph

Sasindran, I believe the OA has to be corrected to

50(Option A)
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