Two men $A$ and $B$ start from a place $P$ walking at $3 \, km/h$ and $3.5 \, km/h$ respectively. How many $km$ will they be apart at the end of $3 \, h$,if they walk in opposite directions (in $.5$)?

$A$ bus takes $15\, hours$ to travel from Delhi to Chandigarh. The bus travels for one-third of the total time at a speed of $80\, km/h$. It travels for $40\%$ of the remaining time at a speed of $70\, km/h$. It travels for $\frac{2}{3}$ of the remaining time at a speed of $85\, km/h$,and the rest of the time at a speed of $100\, km/h$. What is the total distance covered by the bus?

An aeroplane covers a certain distance at a speed of $240 \text{ km/h}$ in $5 \text{ hours}$. To cover the same distance in $1 \frac{2}{3} \text{ hours}$,it must travel at a speed of (in $\text{km/h}$):

$A$ man walks a certain distance and rides back in $4 \, h \, 30 \, min$. He could ride both ways in $3 \, h$. The time required by the man to walk both ways is?

$A$ train takes $18 \, s$ to pass completely through a station $162 \, m$ long and $15 \, s$ through another station $120 \, m$ long. The length of the train (in $m$) is:

Two trains start from $P$ and $Q$ respectively and travel towards each other at a speed of $50\, km/hr$ and $40\, km/hr$ respectively. By the time they meet,the first train has travelled $100\, km$ more than the second. The distance between $P$ and $Q$ is (in $km$):