$A$ 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?

Two trains $250 \; m$ and $200 \; m$ long are running on parallel tracks at the rate of $36 \; km/hr$ and $45 \; km/hr$ respectively. In how much time (in $sec$) will they cross each other,if they are running in the same direction?

Two trains $100 \; m$ and $120 \; m$ long are running in the same direction with speeds of $72 \; km/h$ and $54 \; km/h$. In how much time will the faster train cross the second (in $; s$)?

Two trains of equal length are running on parallel tracks in the same direction at $46 \; km/h$ and $36 \; km/h$ respectively. The faster train passes the slower train in $36 \; seconds$. The length (in $m$) of each train is:

Two trains running at the rate of $45 \; km/h$ and $36 \; km/h$ respectively,on parallel tracks in opposite directions,are observed to pass each other in $8 \; seconds$. When they are running in the same direction at the same rate as before,a person sitting in the faster train observes that he passes the other in $30 \; seconds$. Find the length of the trains (in $m$).

Two trains are running at $40 \; km/hr$ and $20 \; km/hr$ respectively in the same direction. The faster train completely passes a man in the slower train in $5 \; seconds$. What is the length (in $m$) of the faster train?