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

$A$ train running at a speed of $40 \, m/s$ crosses a pole in $21 \, s$ less than the time it requires to cross a bridge $3.5$ times its length at the same speed. What is the length of the bridge (in $m$)?

$A$ student goes to school at the rate of $2 \frac{1}{2} \text{ km/h}$ and reaches $6 \text{ min}$ late. If he travels at the speed of $3 \text{ km/h}$,he is $10 \text{ min}$ early. The distance (in $\text{km}$) between the school and his house is:

$A$ train leaves station $A$ at $7 \, am$ and reaches station $B$ at $11 \, am$. Another train leaves station $B$ at $8 \, am$ and reaches station $A$ at $11.30 \, am$. At what time do the two trains cross each other?

If a train runs at $40 \text{ km/h}$,it reaches its destination late by $11 \text{ minutes}$,but if it runs at $50 \text{ km/h}$,it is late by $5 \text{ minutes}$ only. Find the correct time for the train to complete its journey (in minutes).

$A, B$ and $C$ start together from the same place to walk around a circular path of length $12 \, km$. $A$ walks at the rate of $4 \, km/h$,$B$ at $3 \, km/h$,and $C$ at $\frac{3}{2} \, km/h$. They will meet together at the starting place at the end of (in $h$):