$A$ 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 $\text{km/h}$)

$A$ man on tour travels the first $160 \, km$ at $64 \, km/hr$ and the next $160 \, km$ at $80 \, km/hr$. What is the average speed for the first $320 \, km$ of the tour (in $km/hr$)?

$A$ $135\, m$ long train is running with a speed of $54\, km/h$. In what time will it pass a telegraph post? (in $seconds$)

The ratio between the speed of a train and a car is $16: 15$. Also,a bus covered a distance of $480 \, km$ in $8 \, hours$. The speed of the bus is $\frac{3}{4}$ the speed of the train. How much distance will the car cover in $6 \, hours$? (in $km$)

$A$ man covers a certain distance by car driving at $70 \, km/hr$ and he returns to the starting point riding on a scooter at $55 \, km/hr$. Find his average speed for the whole journey in $km/hr$.

$A$ train of length $100\, m$ crosses another train of length $150\, m,$ running on a parallel track in the opposite direction in $9\, s.$ If the speed of the train having length $150\, m$ is $40\, km/h,$ what is the speed (in $km/h$) of the other train?