$A$ person covers a certain distance in $6 \, hours$ if he travels at $40 \, km/h$. If he has to cover the same distance in $4 \, hours$,then his speed must be (in $km/h$):

$A$ man travelled a distance of $80\, km$ in $7\, hours$,partly on foot at the rate of $8\, km/h$ and partly on bicycle at $16\, km/h$. The distance travelled on foot is (in $km$):

$A$ $180 \, m$ long train crosses another $270 \, m$ long train running from the opposite direction in $10.8 \, s$. If the speed of the first train is $60 \, km/h$,what is the speed of the second train in $km/h$?

$A$ motor car completes a journey in $10 \, hours$. It covers the first half of the distance at $21 \, km/h$ and the remaining half at $24 \, km/h$. Find the total distance (in $km$).

Two cyclists started simultaneously towards each other and meet each other $3$ hours $20$ minutes later. How much time will it take the slower cyclist to cover the whole distance if the first arrived at the place of departure of the second $5$ hours later than the second arrived at the point of departure of the first? (in hours)

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 $km$)