Two trains 140 m and 160 m long run at the speed of 60 km/hr and 40 km/hr respectively in opposite directions on parallel tracks. The time (in seconds) which they take to cross each other, is:

Given Data

• Train lengths = 140 m and 160 m
• Speeds = 60 km/hr and 40 km/hr
• Opposite directions
• Required: time to cross each other

Step 1: Relative speed and distancev_rel = 60 + 40 = 100 km/hr = 100 × (5/18) = 27.7778 m/sDistance = 140 + 160 = 300 m

Step 2: Timet = 300 ÷ 27.7778 = 10.80 s (rounded to 2 decimals)

Checks & Common Pitfalls

• Use the sum of speeds for opposite directions.
• Keep units consistent before dividing.

Final AnswerThey take 10.80 s to cross.