Question

a train crosses a pole in 15 seconds and a 100m. long platform in 25 seconds what is is th length of the train

Answer 1

Considering uniform velocity
let the length of train be x
so velocity = displacement/ time
v=x/15
for pole
Now for platform
v=(100)+x/25
dividing both equations
x/(100+x)=15/25
25x=1500+15x
10x=1500
x=150m
Answer is 150m
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Answer 2

hye

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Let the length of the train is x meter and Speed of the train is y meter/second


Then x/y = 15 [because distance/speed = time] 


=> y = 15/x

=>$\frac{x+100}{25} = \frac{x}{15}$

=>x = 150 metres

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hope it helps u