Trains A and B, 100 m and 60 m long, move in opposite directions. The shorter train has speed three times the longer train. They take 4 s to completely cross. Their speeds are:
Options

Question

Trains A and B, 100 m and 60 m long, move in opposite directions. The shorter train has speed three times the longer train. They take 4 s to completely cross. Their speeds are:

G1 Physics · Accepted Answer

Total relative distance for complete crossing =100+60=160 m. Relative speed=160/4=40 m s⁻¹. If the shorter train has three times the speed of the longer train, let speeds be 3v and v. Since they move oppositely, 4v=40, giving v=10 m s⁻¹ and 3v=30 m s⁻¹. Hence option A. The printed source key appears inconsistent.