Question

A train speeds past a pole in 15 seconds and speed past a platform of 100 meters in 30 seconds.its length in meters is

Answer 1

speed=train length/time
x/15
we know that train Cross time 30 sec
time=D/S
30=(x+100)/(X/15)
2X=x+100
x=100

Answer 2

Answer:

The Length of train is 100 m

Step-by-step explanation:

Let the length of the train be x

A train speeds past a pole in 15 seconds

Time = 15 seconds

Distance = x

$Speed =\frac{distance}{Time}$

$Speed =\frac{x}{15}$   ------1

A train speeds  past a platform of 100 meters in 30 seconds.

Time = 30 seconds

Distance =Length of train +Length of platform = x+100

$Speed =\frac{Distance}{Time}$

$Speed =\frac{x+100}{30}$   ------2

Now with 1 and 2

$\frac{x}{15} =\frac{x+100}{30}$

$\30x =15x+1500$

$15x=1500$

$x=100$

Hence The Length of train is 100 m