Aptitude - Problems on Trains - Discussion

Why it's taken x-1 but not x+1 because train 2 starts 1 hr later?

Why it's taken x-1 but not x+1 because train 2 starts 1 hr later?

60 km as relative speed of both the trains is 100 km/hr and
distance = 100km.

Then time taken to meet = distance/speed(relative).
T = 100/100 = 1 hr

So the trains will meet each other after 1 hour so,
Distance covered by first train in 1 hour = 60km/hr * 1hr = 60 km,
Distance covered by second train in 1 hour = 40km/hr * 1hr = 40 km,
Therefore, the distance from station A where both trains will meet = 60km.

Distance between two stations A and B is 100 km, two trains with speed 60 km/h and 40 km/h are running towards each other. What is the distance from station A where both trains will meet?

Can anyone find the answer?

Simple formula to be remembered.

Total Time Taken = (d = s2 * t)/s1 + s2.

Where d = 110km, s2 = 25kmph, s1 = 20kmph, t = (8:00am - 7:00am) = 1hr.
From that we get 3hrs.

Therefore required Time is (7:00am + 3hrs) = 10:00Am.

Thanks @Manish Dabhi.

Your explanation is very useful.

Here, the first train is started at 7:00 am at 20 km/h and the second train started at 8 am at the speed of 25 km/ h.

Train first started at 7 am @ 20 km/h.

7 am to 8 am covers =20 km
8 am to 9 am covers = 40 km
9 am to 10 am covers =60 km
10 am to 11am covers = 80km
11 am to 12 it covers 100 km


Train second started at 8am @ 25 km/h.

8 am to 9 am train covers = 25 km
9 am to 10 am it covers = 50 km
10 am to 11 am it covers = 75 km
11 am to 12 it covers = 100km

Now, both it covers 100 km at 12 o'clock. then how these 2 train meets each other at 10 am please help me, sir.

@ANISH MISHRA: Let the speed of the train P be xkm/hr and Q be ykm/hr.

After 6hrs, P would have travelled 6xkm (distance=speed*time) and similarly Q would have travelled 6ykm. Given, the distance between P and Q is 528, Hence,

6x + 6y = 528 -> (i).

Also, given that P having travelled 8km/hr more than Q. So,
x = y + 8 -> (ii).

Solving equation (i) & (ii),

x = 48km/hr (speed of train P).
y = 40km/hr (speed of train Q).

@Yuvaraj, Thanks.

If the train was late by 3 hours and 12 minutes, then calculate the nearest hours.