Question

A train is travelling from a station A to another station B at a speed of 60 km/hr. Another train is travelling at a speed of 30 km/hr from station B to A. The relative speed of train A with respect to B is​

Answer 1

Answer:

Correct option is

B

68.57 kmph

Let the distance A and B be x km

Speed while going =60 kmph

∴ time required to go =60xhr

Speed while returning =80 kmph

∴ time required to return =80xhr.

∴ total time required =(60x+80x)hr=2407xhr.

And, total distance travelled =2x km

∴Average velocity=2407x2xkmph=68.57kmph

Answer 2

Concept:

Relative speed is the speed rate at which two vehicles or bodies are going away from / coming closer to each other. And, When trains move in the opposite direction then their relative speed is given by the sum of their speed.

Given:

Speed of  train A = 60 km/hr

Speed of  train B = 30 km/hr

Find:

We are asked to seek out the relative speed of train A with respect to B.

Solution:

We have,

Speed of  train A = 60 km/hr

Speed of  train B = 30 km/hr

Now,

When trains move in the opposite direction then their relative speed is given by the sum of their speed,

i.e.

The relative speed of train A with respect to B =  60 + 30 = 90 km/hr

Hence we can say that the relative speed of train A with respect to train B  is 90 km/hr.

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