$A$ train speeds past a pole in $15 \, \text{seconds}$ and speeds past a $100 \, \text{meters}$ long platform in $25 \, \text{seconds}$. Its length in meters is:

Buses start from a bus terminal with a speed of $20 \text{ km/h}$ at intervals of $10 \text{ mins}$. What is the speed of a man coming from the opposite direction towards the bus terminal if he meets the buses at intervals of $8 \text{ mins}$? (in $\text{km/h}$)

$A$ motor car completes a journey in $10 \, hours$. It covers the first half of the distance at $21 \, km/h$ and the remaining half at $24 \, km/h$. Find the total distance (in $km$).

$A$ person covers half of his journey at $30 \text{ km/h}$ and the remaining half at $20 \text{ km/h}$. The average speed for the whole journey is (in $\text{km/h}$)

$A$ 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 $\text{km}$):

$A$ thief is noticed by a policeman from a distance of $200\, m$. The thief starts running and the policeman chases him. The thief and the policeman run at the speed of $10\, km/h$ and $11\, km/h$ respectively. What is the distance between them after $6\, minutes$? (in $m$)