Two trains are moving in opposite directions @ 60 km/hr and 90 km/hr. Their lengths are 1.10 km and 0.9 km respectively. The time taken by the slower train to cross the faster train in seconds is:

Given Data

• Speeds = 60 km/hr and 90 km/hr (opposite directions)
• Lengths = 1.10 km and 0.9 km
• Required: time for slower train to cross the faster train

Step 1: Use relative speed and total distanceRelative speed (opposite directions) = 60 + 90 = 150 km/hrTotal distance to cross completely = 1.10 + 0.90 = 2.00 kmTime (in hours) = distance ÷ speed = 2.00 ÷ 150 = 1/75 hr

Step 2: Convert hours to seconds1 hour = 3600 sTime = (1/75) × 3600 = 48 s

Checks & Common Pitfalls

• For opposite directions add speeds.
• For complete crossing add lengths.
• Convert hours to seconds carefully.

Final AnswerThe time taken is 48 s.