Aptitude - Problems on Trains - Discussion

Soln,
L.t -130m ,s -45km/hr ,t -30 sec
L.b - ?.

Let us assume length of the bridge as x,
D = s* t.

130 (l.t) + x(l.b) = 45 km/hr * 30 sec.
130 + x =45 * 5/18 m/ sec * 30 sec.

After solving we will get,
130 + x = 375,
x = 375 -130,
x = 245 m.
So, the length of the bridge is 245 m.

Given, train length s = 130.
Let, the bridge length is x.
Total passing length = velocity * time.
S + x = vt.
130 + x = 45 * (5/18) * 30.
x = 245m.

@Rajesh.

We take 5/18 to convert from km/h into m/s.

Given, train length s = 130.
Let, the bridge length is x.
Total passing length = velocity * time.
S + x = vt.
130 + x = 45 * (5/18) * 30.
x = 245m.

Why are you people adding the bridge distance?

If in case the bridge distance is lesser than the train distance, then how it will be calculated?

To convert kilometres per hour (km/hr) to meters per second (m/sec), we use the conversion factor of 5/18. This conversion factor is derived from the relationship between kilometres and meters, as well as hours and seconds.

Here's the breakdown of the conversion:

1 kilometer = 1000 meters.
1 hour = 3600 seconds.

To convert km/hr to m/sec, we need to cancel out the kilometres and hours units while retaining the meters and seconds units. We can do this by multiplying the value in km/hr by a conversion factor that equates to 1.

To convert kilometres to meters, we multiply by 1000 (since 1 kilometre is equal to 1000 meters). This step cancels out the kilometres unit.

To convert hours to seconds, we multiply by 3600 (since 1 hour is equal to 3600 seconds). This step cancels out the hours unit.

So, the conversion factor becomes:
(1000 meters/1 kilometer) * (1 hour/3600 seconds)

Simplifying this expression gives us:
(1000/1) * (1/3600) = 1000/3600 = 5/18.

Hence, multiplying the value in km/hr by 5/18 will convert it to m/sec.

How do you get 25/2? Explain, please.

Why do we take 5/18, anyone, please Explain it?

How 5/18 came? Please explain to me.

l = ?
Train length =130m
Speed = 45km/hr
Time = 30s.

30s = time(130+l(m)).
30s = (130+l)m/45km/hr.
30s = (130+l)m/45 * 5/18m/s.
30s = 130+l/(25/2)m/s.

30s = (130+l) * 2/25.
30 * 25 = (130 +l)* 2.
15*25 = 130 + l.
375 - 130 = l.
245m = l.