Question

Two trains 350 m and 250 m long are going at 42 km and 30 km per hour respectively in opposite direction. How long would it take them to pass each other ?

Answer 1

Distance = (350+250)m = 600 m
Relative speed $=(42+30)$km/hr
$=72$km/hr
$=\frac{(72\times 1000)}{60\times 60}m/s$
$=20$ m/s
Time = distance/speed
$=\frac{600}{20}$ s
$=30$ s