Question

Two passenger trains are traveling in opposite direction. the distance between them is 110 kms. one of them starts at 4 am and the other starts at 5 am on a velocity of 20 and 25 kmph respectively.what is the time when they both will meet?

Answer 1

distance between them is 110 km.
let the train A started at 4am at 20 kmph
and train B started at 5am with 25kmph speed.
=>distance travelled by train A in 1 hour(4am-5am).= 20×1= 20 km
remaining distance between them is now = 110-20 = 90 km.
now train A us moving with a velocity of 20 km/h and train B is moving with 25km/h
so the relative velocity between them = Velocity of A-(- velocity of B,) ,as they are moving in opposite direction.
so relative velocity = 20-(-25)
=> 20+25 =45 km/h
time taken to meet= (distance between them)/ (relative velocity)
=> 90/45= 2 hrs
so ,they will meet after two hours of staring of train B
which is 7am.