$A$ car covers the first $39 \, km$ of its journey in $45 \, minutes$ and the remaining $25 \, km$ in $35 \, minutes.$ What is the average speed of the car (in $km/h$)?

$A$ 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 $AM$):

$A$ train leaves the station $1 \, hr$ before the scheduled time. The driver decreases its speed by $4 \, km/hr$. At the next station $120 \, km$ away,the train reaches on time. Find the original speed of the train in $km/hr$.

$A$ 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 $km/hr$.

$A$ car traveling at a speed of $40 \, km/h$ can complete a journey in $9 \, hours$. How long will it take to travel the same distance at $60 \, km/h$? (in $hours$)

Two trains are moving in the same direction at $50 \text{ km/hr}$ and $30 \text{ km/hr}$. The faster train crosses a man sitting in the slower train in $18 \text{ seconds}$. Find the length of the faster train in meters.