$A$ train goes from Ballygunge to Sealdah at an average speed of $20 \text{ km/h}$ and comes back at an average speed of $30 \text{ km/h}$. The average speed of the train for the whole journey is (in $\text{km/h}$)

$A$ train leaves station $A$ at $5\, AM$ and reaches station $B$ at $9\, AM$ on the same day. Another train leaves station $B$ at $7\, AM$ and reaches station $A$ at $10.30\, AM$ on the same day. The time at which the two trains cross one another is (in $AM$):

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

$A$ man travels $360 \, km$ in $4 \, hrs$,partly by air and partly by train. If he had travelled all the way by air,he would have saved $\frac{4}{5}$ of the time he was in train and would have arrived at his destination $2 \, hrs$ early. Find the distance he travelled by train (in $km$).

$A$ train running at the speed of $66 \, km/h$ crosses a signal pole in $18 \, seconds$. What is the length of the train (in $m$)?

Flight $A$ usually takes $1 \, \text{hour}$ more than Flight $B$ to travel a distance of $7200 \, \text{km}$. Due to engine trouble,the speed of Flight $B$ decreases by a factor of $\frac{1}{6}$,so it takes $36 \, \text{minutes}$ more than Flight $A$ to complete the same journey. What is the speed of Flight $A$ (in $\text{km/hr}$)?