$A$ boy goes to his school from his house at a speed of $3 \text{ km/hr}$. If he takes $5 \text{ hours}$ in total for going and coming back,the distance between his house and school is (in $\text{km}$):

$A$ man on tour travels the first $160 \, km$ at $64 \, km/hr$ and the next $160 \, km$ at $80 \, km/hr$. What is the average speed for the first $320 \, km$ of the tour (in $km/hr$)?

Two trains start at the same time from two stations and proceed towards each other at the speeds of $20 \, km/h$ and $25 \, km/h$ respectively. When they meet,it is found that one train has travelled $80 \, km$ more than the other. Find the distance between the two stations (in $km$).

How many $km/h$ does a man walk who passes through a street $600 \, m$ long in $5 \, minutes$?

$A$ $135\, m$ long train is running with a speed of $54\, km/h$. In what time will it pass a telegraph post? (in $seconds$)

$A$ train can travel $50\%$ faster than a bus. Both start from point $A$ at the same time and reach point $B$ at the same time. Point $B$ is $75 \, km$ away from point $A$. On the way, the train stops for $12.5 \, minutes$. The speed of the bus is (in $km/h$):