$A$ train is moving with a speed of $180 \, km/hr$. Its speed in $m/s$ is:

$A$ motorcyclist left $6 \frac{2}{3}$ minutes later than the scheduled time,but in order to reach his destination $21 \, km$ away on time,he had to increase his speed by $12 \, km/h$ from his usual speed. What is the usual speed (in $km/h$) of the motorcyclist?

Ravi and Ajay start simultaneously from a place $A$ towards $B$,$60 \, km$ apart. Ravi's speed is $4 \, km/h$ less than that of Ajay. Ajay,after reaching $B$,turns back and meets Ravi at a place $12 \, km$ away from $B$. Ravi's speed is (in $km/h$):

On a tour,a man travels at the rate of $64 \text{ km/h}$ for the first $160 \text{ km}$,then travels the next $160 \text{ km}$ at the rate of $80 \text{ km/h}$. The average speed in $\text{km/h}$ for the first $320 \text{ km}$ of the tour is:

Two trains start at the same time from Mumbai and Pune and proceed towards each other at the speeds of $60\, km/h$ and $40\, km/h$, respectively. When they meet, it is found that one train has travelled $20\, km$ more than the other. Find the distance between Mumbai and Pune (in $km$).

$A$ and $B$ are two towns. $A$ car goes from $A$ to $B$ at a speed of $64 \, km/h$ and returns to $A$ at a slower speed. If its average speed for the whole journey is $56 \, km/h$,find its return speed (in $km/h$).