Relative Speed = Speed of Train 2 - Speed of Train 1 (as both trains are moving in the same direction) Time = Distance ∕ Speed Calculation: Distance to be covered = Length of Train 1+ Length of Train 2 =170+480=650m Relative Speed = Speed of Train 2− Speed of Train 1 =80−70=10km∕h Convert relative speed to m∕s : Relative Speed =10×(1000∕3600)=10×5∕18=50∕18m∕s Time = Distance ∕ Speed ⇒ Time =650∕(50∕18) ⇒ Time =650×(18∕50) ⇒ Time =(650×18)∕50 ⇒ Time =11700∕50 ⇒ Time =234 seconds Convert time to minutes: ⇒ Time =234∕60=3.9 minutes