$A$ 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 $km/h$):

$A$ person covers half of his journey at $30 \text{ km/h}$ and the remaining half at $20 \text{ km/h}$. The average speed for the whole journey is (in $\text{km/h}$)

The average speed of a car is $1 \frac{4}{5}$ times the average speed of a bus. $A$ tractor covers $575 \text{ km}$ in $23 \text{ hours}$. How much distance will the car cover in $4 \text{ hours}$ if the speed of the bus is twice the speed of the tractor? (in $\text{km}$)

$A$ car covers a distance of $330 \, km$ in a certain amount of time at a speed of $55 \, km/h$. What is the average speed of a bike that covers a distance of $15 \, km$ less than the car in $1 \, hour$ less than the time taken by the car? (in $km/h$)

$A$ and $B$ are two stations. $A$ train goes from $A$ to $B$ at $64 \text{ km/h}$ and returns to $A$ at a slower speed. If its average speed for the whole journey is $56 \text{ km/h}$,at what speed did it return? (in $\text{km/h}$)

The diameter of each wheel of a car is $70 \, cm$. If each wheel rotates $400 \, \text{times per minute}$, then the speed of the car (in $km/hr$) is $\left( \text{Take } \pi = \frac{22}{7} \right)$.