Aptitude - Problems on Trains - Discussion

Distance =speed *time,
D=120+80km/h*9,
D=200*5/18*9,
D=1000/2,
D=500-270=230m.

Please, tell me when to find relative speed?

Relative speed is to be found when two moving objects or trains are given.

What will happen if both trains are in the same direction as we relative velocity we can subtract but how the equation will come?

Please tell me.

If we want to find kmph means 15/8.
mph means 8/15 simple formula.

On cross multiplication we get,

9 (500) =4500.
Then, 9 (270+x), 9 goes to another side.
270+x=4500/9,
270+x=500,
X=500-270.

Finally, we get 230.

What we know is:

t1 length=270m.
t1 speed = 120km/h or 33.33m/s.
t2 length = x,
t2 speed = 80km/h or 22.22m/s.
total speed = 9 seconds.

We need to find the relative speed, so its done like this because the trains are moving towards each other.

33.33m/s+22.22m/s = 55.55m/s.

Now we have all the information we need to solve the length of train 2.

270m+Xm
-------------- = 9s.
55.55m/s

Now we find the total length of both trains combined. We use the information we have. 55.55m/s is now converted to its opposite function, from division to multiplication. 55.55m/s * 9s = 499.95m.

So 499.95m is the total length of both trains combined, so now we can solve train 2's length by completing this final equation.

x= 499.95m-270m = 229.95m. round up to 230m, therefore train 2's length is 230m.

Train Length=270m.
Speed=120km/h=120*(5/18)=32.4m/s.

Time= 9.

Train2 Length= X.
Speed of Train2=80km/h=80*(5/18)=21.6.

Relative Speed=32.4+21.6=54.00.
Relative Length=270 + X.

Speed=Distance/Time.
54=(270+X)/9.

(54*9)-270=X.

X=216.

Then How come 230?

how we take x+270÷9? Please explain.

Step-1:

Distance = 250m,
Speed = 72*5/18 = 20,
Time = 26 sec.

Step-2:
Formula d=s*t,
250m=20*26,
250m = 520,
M= 520- 250.
m =270 ans.