A train passes a station platform in 36 seconds and a man standing on the platform in 20 seconds. If the speed of the train is 54 km/hr, what is the length of

A. 120
B. 260
C. 240
D. 220

Explanation with best method.
5 Steps
1.Data:
Train station platform= 36Sec
Standing platform = 20Sec
Speed of train = 54km/hr
2.Required:
Length of platform= x=???
3.Formula:
X+length of train/Train station platform
4.Solution: first for terms
Speed = 54 ×1000m/3600sec = 15 m/Sec.
Length of the train = (15 m/Sec × 20Sec = 300 m.
Let the length of the platform be x metres.
Now, x + 300m /36Sec= 15 m/Sec
x+300m= 15m/Sec×36Sec
x + 300m = 540m
x= 540m-300m
x = 240 m.
5.Result:
Length of platform=x=240m