$A$ man travels first $50 \, km$ at $25 \, kmph$, next $40 \, km$ at $20 \, kmph$, and then $90 \, km$ at $15 \, kmph$. His average speed for the whole journey (in $kmph$) is:

$A$ man leaves a point $P$ and reaches the point $Q$ in $4 \, hours$. Another man leaves the point $Q$,$2 \, hours$ earlier and reaches the point $P$ in $4 \, hours$. Find the time in which the first man meets the second man (in $hours$).

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 $km$).

The ratio of the speeds of a car,a jeep,and a tractor is $3:5:2$. The speed of the jeep is $250\%$ of the speed of the tractor,which covers $360\,km$ in $12\,hours$. What is the average speed of the car and the jeep together? (in $km/h$)

The ratio between the speed of a bike and a train is $15:27$ respectively. Also,a bus covers a distance of $720 \, km$ in $9 \, hours$. The speed of the bike is three-fourths the speed of the bus. How much distance will the train cover in $7 \, hours$? (in $km$)

$A$ and $B$ are $20 \text{ km}$ apart. $A$ can walk at an average speed of $4 \text{ km/hr}$ and $B$ at $6 \text{ km/hr}$. If they start walking towards each other at $7 \text{ a.m.}$,when will they meet? (in $\text{a.m.}$)