Two trains are running in opposite directions with the same speed. If the length of each train is 120 metres and they cross each other in 12 seconds, then the speed of each train (in km/hr) is:

Given Data

• Two trains in opposite directions with the same speed
• Each train length = 120 m
• They cross completely in 12 s
• Required: speed of each train (km/hr)

Step 1: Use relative speed and distanceLet each speed = v m/s ⇒ relative speed = 2v m/s.Total distance to cross = 120 + 120 = 240 m.12 = 240 ÷ (2v) ⇒ 2v = 20 ⇒ v = 10 m/s

Step 2: Convert to km/hr10 × (18/5) = 36 km/hr

Checks & Common Pitfalls

• Opposite directions ⇒ add speeds.
• Crossing requires sum of lengths.

Final AnswerEach train's speed is 36 km/hr.