$A$ car travels the first $39 \, km$ distance in $45 \, minutes$ and the next $25 \, km$ distance in $35 \, minutes$. What is its average speed in $km/h$?

$A$ man goes from $A$ to $B$ at a uniform speed of $12 \, km/h$ and returns with a uniform speed of $4 \, km/h$. His average speed (in $km/h$) for the whole journey is?

$A, B$ and $C$ start together from the same place to walk around a circular path of length $12 \, km$. $A$ walks at the rate of $4 \, km/h$,$B$ at $3 \, km/h$,and $C$ at $\frac{3}{2} \, km/h$. They will meet together at the starting place at the end of (in $h$):

$A$ train $200 \, m$ long is running at a speed of $20 \, m/s$. In how much time (in $seconds$) will it cross a bridge of $400 \, m$ length?

It takes $8\, hours$ for a $600\, km$ journey,if $120\, km$ is done by train and the rest by car. It takes $20\, minutes$ more,if $200\, km$ is done by train and the rest by car. The ratio of the speed of the train to that of the car is

$A$ $100\, m$ long train completely passes a man walking in the same direction at $6\, km/h$ in $5\, s$ and also a car travelling in the same direction in $6\, s$. At what speed was the car travelling? (in $km/h$)