Correct Answer - Option 4 : 9.00 a.m.
Given :
Two stations A and B are 80 km apart
Train from A starts at 7 a.m with speed of 20 kmph
Train from B starts at 8 a.m with speed of 40 kmph
Concept used :
Relative speed
If vehicles are moving in opposite direction then speeds are added
if vehicles are moving in same direction then speeds are subtracted
Calculations :
Train A starts at 7 a.m with speed of 20 kmph
Distance covered by train in 1 hour = 20 × 1 (Distance = speed × time)
⇒ 20 km
Now at 8 a.m distance between stations = 80 - 20 = 60 km
Now time taken after 8 a.m when both trains will meet = (Distance/speed)
⇒ 60/(20 + 40) (speeds are added because they are moving in opposite direction)
⇒ 60/60
⇒ 1 hour
Train will meet 1 hour after 8 a.m
∴ Both the trains will meet at 9 a.m