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 $.5$)?

$A$ train is moving with a speed of $180 \, km/hr$. Its speed in $m/s$ is:

$A$ $280 \, m$ long train moving with an average speed of $108 \, km/h$ crosses a platform in $12 \, seconds$. $A$ boy crosses the same platform in $10 \, seconds$. What is the speed of the boy in $m/s$?

Two friends started for a place,one by motorcycle and the other by train. The speed of the motorcycle is $30 \, km/h$ and that of the train is $24 \, km/h$. The first one takes $6 \, hr \, 12 \, min$ to reach the destination. Find the time taken by the second one to reach the destination (in $hr$).

Two trains of equal length take $10\, seconds$ and $15\, seconds$ respectively to cross a telegraph post. If the length of each train is $120\, metres,$ in what time (in $seconds$) will they cross each other when travelling in opposite directions?

If a $200 \, m$ long train crosses a platform of the same length as that of the train in $20 \, s$,then the speed of the train is (in $km/hr$).