$A$ car travelling with $\frac{5}{7}$ of its actual speed covers $42 \, km$ in $1 \, hour \, 40 \, minutes \, 48 \, seconds.$ Find the actual speed of the car (in $km/hr$).

Amit started cycling along the boundaries of a square field from corner point $A$. After half an hour,he reached the corner point $C$,diagonally opposite to $A$. If his speed was $8 \, km/h$,what is the area of the field in square $km$?

$A$ and $B$ are two stations. $A$ train goes from $A$ to $B$ at $64 \text{ km/h}$ and returns to $A$ at a slower speed. If its average speed for the whole journey is $56 \text{ km/h}$,at what speed did it return? (in $\text{km/h}$)

$A$ hare sees a dog $100\, m$ away from her and runs off in the opposite direction at a speed of $12\, km/h$. $A$ minute later,the dog perceives her and gives chase at a speed of $16\, km/h$. How much distance is covered by the hare after being spotted? (in $m$)

With a uniform speed,a car covers a certain distance in $8 \, hours$. Had the speed been increased by $4 \, km/hr$,the same distance could have been covered in $7.5 \, hours$. What is the distance covered? (in $km$)

Two trains are running at a speed of $40 \, km/h$ and $20 \, km/h$ respectively in the same direction. The fast train completely passes a man sitting in the slow train in $5 \, seconds$. The length of the fast train is (in $m$):