Question

Two trains starts from stations A and B respectively with speeds 5 kmph and 10 kmph. Distance between two stations Is 20km. How far apart are they two minutes before they collide?
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Answer 1

Answer:

¼

Step-by-step explanation:

We can simply calculate the distance traveled for one min , as the final distance is same as the distance in that one min

d = s* t

d = (5+10) * 1/60 = 15 / 60 = 1/4 km

OR

So,name the two trains... train A=5km/hr and train B=10km/hr.

We first find the time taken by them to collide.For this we require the concept of relative speed.

Using the relative speeds formula-When two objects move in opposite directions,their relative speeds add up.

We get, Time after which they collided=Distance between them/Relative speed

=20km/(10+5)km/hr=4/3hr=80 mins

Questions says-1 minute before they collided,ie-79 mins.

We find the distance traveled by train A and train B in 79 mins and subtract it from the total distance.This would give the distance between the two bodies one minute before colliding.

Train A(Distance traveled in 79mins)=79x5/60=79/12 km

Train B(Distance traveled in 79mins)=79x10/60=79/6 km

Distance between train A and train B=20km(Total Distance)-(79/12+79/6)

=20-237/12

=1/4