Relative speed and train problems – UGC NET Question

A is correct since opposing motions add speeds, and B is correct as same-direction relative speed is the difference between speeds. C is true because when trains cross, they must cover the sum of their lengths relative to each other. E is also correct because the units are consistent so distance is directly in kilometres. D is false because distance is speed × time, not speed ÷ time. Hence the combination A, B, C and E only is correct.

Option A:
Option A leaves out E, failing to note the important unit consistency that allows direct interpretation of distance in kilometres. Though it includes true statements, it is not complete.

Option B:
Option B omits A and thus does not mention the case of opposite direction motion, which is central for many train problems. This makes the description insufficient.

Option C:
Option C is incomplete because it leaves out B, ignoring the same-direction relative speed rule, and so does not cover all key cases used in exam questions.

Option D:
Option D is correct, bringing together all true statements and excluding D, which misstates the basic speed–distance relation. It matches the conceptual framework required for time–speed–distance and train problems.