$A$ motor car completes a journey in $10 \, hrs$. It covers the first half of the distance at $21 \, km/hr$ and the second half at $24 \, km/hr$. Find the total distance in $km$.

$A$ train $100 \, m$ long takes $3 \frac{3}{5} \, s$ to cross a man walking at the rate of $6 \, km/h$ in a direction opposite to that of the train. Find the speed of the train in $km/h$.

Two trains,each of length $125 \, m$,are running on parallel tracks in opposite directions. One train is running at a speed of $65 \, km/h$ and they cross each other in $6 \, s$. The speed of the other train is (in $km/h$):

Two men start together to walk a certain distance,one at $4 \, km/h$ and another at $3 \, km/h$. The former arrives half an hour before the latter. Find out the distance in $km$.

$A$ motorcyclist travels from Mumbai to Pune,a distance of $192 \, km$,at an average speed of $32 \, km/h$. Another man starts from Mumbai by travelling in a car,$2 \frac{1}{2} \, hours$ after the motorcyclist and reaches Pune half an hour earlier. What is the ratio of the speeds of the motorcycle and the car?

Supposing that telegraph poles on a railroad are $50 \, m$ apart,how many will be passed by a train in $4 \, hours$ if the speed of the train is $45 \, km/h$?