Two trains of equal lengths take $10 \; s$ and $15 \; s$ respectively to cross a telegraph post. If the length of each train is $120 \; m$,in what time (in $s$) will they cross each other when travelling in opposite directions?

$A$ train speeds past a pole in $15 \; \text{seconds}$ and a platform $100 \; \text{m}$ long in $25 \; \text{seconds}$. Its length is (in $\text{m}$):

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 $; s$)?

$A$ goods train runs at the speed of $72 \; km/h$ and crosses a $250 \; m$ long platform in $26 \; seconds$. What is the length (in $m$) of the goods train?

Two goods trains,each $500 \; m$ long,are running in opposite directions on parallel tracks. Their speeds are $45 \; km/hr$ and $30 \; km/hr$ respectively. Find the time (in $seconds$) taken by the slower train to pass the driver of the faster one.

$A$ train $110 \;m$ long is running with a speed of $60 \;km/h$. In what time (in $seconds$) will it pass a man who is running at $6 \;km/h$ in the direction opposite to that in which the train is going?