$A$ car covers four successive $3 \, km$ stretches at speeds of $10 \, km/h$,$20 \, km/h$,$30 \, km/h$,and $60 \, km/h$ respectively. Its average speed over this total distance is (in $km/h$):

The distance between two cities $A$ and $B$ is $330\, km$. $A$ train starts from $A$ at $8\, a.m.$ and travels towards $B$ at $60\, km/hr$. Another train starts from $B$ at $9\, a.m.$ and travels towards $A$ at $75\, km/hr$. At what time do they meet? (in $a.m.$)

An athlete runs a $200$ $\text{meters}$ race in $24$ $\text{seconds}$. His speed is (in $\text{km/hr}$):

$A$ 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?

$A$ person started his journey in the morning. At $11:00 \, am$ he covered $\frac{3}{8}$ of the journey and on the same day at $4:30 \, pm$ he covered $\frac{5}{6}$ of the journey. He started his journey at ..... $am$

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 $km$).