Aptitude - Problems on Trains - Discussion

Solution:

45 * 5/18 = 12.5,
12.5 * 30 = 375,
375 - 130 = 245,
So, this is how we get 245.

45km In 1 hr.
45km In 60 min.
45 km In 60*60 seconds
45000m In 60*60 seconds
45000/120 In 30 seconds
375.m in 30 seconds.
375m including with train length so the train length is;
375 - 130 = 245 m ANS.

Distance travelled by Train= length of bridge + length of the train
So, x + 130m.
Speed = 45km/hr = 45 * 5/18 = 25/2 m/s.
Distance = speed * time.
25/2 * 30,
= 245m.

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.

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

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 TD = 130m, speed = 45km/h, Time = 30sec.
And Length of the Station = x.

speed = 45*5/18 .
=225/18.
So, the speed =25/2.

know the length of the station,
x + TD = speed * Time
x + 130 = 25/2 * 30
x + 130 = 12.5 * 30
x + 130 = 375.
x = 375 - 130,
Final x = 245.
The correct answer is option C.

4.5x 5/18 = 12.5
12.5 x 30 = 375
375 - 130 = 245 ans.

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?

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