$A$ train $100 \; m$ long is running at the speed of $30 \; km/hr$. Find the time (in $sec$) taken by it to pass a man standing near the railway line.

$A$ train passes a station platform in $36 \; \text{seconds}$ and a man standing on the platform in $20 \; \text{seconds}$. If the speed of the train is $54 \; \text{km/hr}$, what is the length (in $m$) of the platform?

How many seconds will a $500 \;m$ long train take to cross a man walking with a speed of $3 \;km/h$ in the same direction as the moving train,if the speed of the train is $63 \;km/h$?

Two trains running in opposite directions cross a man standing on the platform in $27 \;seconds$ and $17 \;seconds$ respectively, and they cross each other in $23 \;seconds$. The ratio of their speeds is

$A$ $300 \;m$ long train crosses a platform in $39 \;seconds$,while it crosses a signal pole in $18 \;seconds$. What is the length of the platform? (In $m$)

$A$ train $75 \; m$ long overtook a person who was walking at the rate of $6 \; km/h$ and passed him in $7 \frac{1}{2}$ seconds. Subsequently,it overtook a second person,and passed him in $6 \frac{3}{4}$ seconds. At what rate (in $km/h$) was the second person travelling?