Aptitude - Problems on Trains - Discussion

60 * (5/18) = 50/3.
Speed = Distance/ Time.
Distance = Speed * Time = (50/3) * 9,
= 150 m.

How 5/18 came I will explain.

1 km = 1000 m.
1hr = 60min.
1 min = 60sec.
60min = 3600 sec.
1000/3600 = 5/18.
(Cancelling two zeroes up and down and 2*5 = 10 and 2*18=36).

Why we are calculating 5/18 not 18/5? Please explain it.

Convert km to m - 60000.
Convert hr to sec - 3600.

Sso, 60000/3600 = 16.666(speed) * 9 (time) = 150.

Data:
T=9,
S=?,
L=?

Time = length/seconds.
S = 60*5/18.
S = 16.6666,
T = L/S.
9 = L/16.6666,
L = 9×16.6666,
L = 149.9,
L = 150.

Should any one tell me how 5/18 came here?

Where,
Speed = Distance(s)/Time(t).
To convert speed into m/s from km/hr.
Then, use the formula = Speed x Time = 100/6 * 9 = 150m.

@Raj
To convert km to metre;
Km - m = × 5/18.
m - km = × 18/5.

I still don't understand. How 5/18 came? Please explain to me.

To know: If the train crosses the pole.
The total distance travelled by train would be its length.
To do: So, calculate the distance travelled by the train to cross the pole.
Formula: Distance(d) = Speed x Time.
Given: Speed of Train 60 km/hr, Time taken to cross a pole = 9 seconds.

Steps:
1. the speed is given in "km/hr" but time is in "Seconds"... Multiplying speed in km/hr directly with time in seconds is not valid.
2. Now, to convert to m/s...
speed = 60 x 5/18 = 16.67 m/s.
3. Distance(d) = 16.67 x 9 = 150 meters.

Final answer: The length of the train is 150 meters.