$A$ $570 \, m$ long train crosses a platform of equal length in $15 \, s$. What is the speed of the train in $m/s$?

$A$ train of length $100\, m$ crosses another train of length $150\, m,$ running on a parallel track in the opposite direction in $9\, s.$ If the speed of the train having length $150\, m$ is $40\, km/h,$ what is the speed (in $km/h$) of the other train?

$A$ train running at $\frac{7}{11}$ of its normal speed reached a place in $22\, \text{hours}$. How much time could be saved if the train had run at its normal speed? (in $\text{hours}$)

$A$ train $180 \, m$ long is running at a speed of $90 \, km/h$. How long will it take to pass a post? (in $sec$)

$A$ bus started its journey from Bettiah and reached Motihari in $44 \, \text{min}$ with an average speed of $50 \, \text{km/h}$. If the average speed of the bus is increased by $5 \, \text{km/h}$, how much time will it take to cover the same distance? (in $\text{min}$)

$A$ train passes two persons walking in the same direction at a speed of $3 \, km/h$ and $5 \, km/h$ respectively in $10 \, s$ and $11 \, s$ respectively. The speed of the train is (in $km/h$):