$A$ train leaves the station $1 \, hr$ before the scheduled time. The driver decreases its speed by $4 \, km/hr$. At the next station $120 \, km$ away,the train reaches on time. Find the original speed of the train in $km/hr$.

$A$ man can reach a certain place in $30 \, \text{hours}$. If he reduces his speed by $\frac{1}{15}^{th}$, he goes $10 \, \text{km}$ less in that same time. Find his speed in $\text{km/hr}$.

$A$ 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 $\text{km/h}$)

$A$ car travels a distance of $75 \, km$ at the speed of $25 \, km/h$. It covers the next $25 \, km$ of its journey at the speed of $5 \, km/h$ and the last $50 \, km$ of its journey at the speed of $25 \, km/h$. What is the average speed of the car? (in $km/h$)

$A$ man walking at $3 \, km/h$ crosses a square field diagonally in $2 \, minutes$. The area of the field (in $m^2$) is:

An express train travelled at an average speed of $100 \, km/hr$, stopping for $3 \, minutes$ after every $75 \, km$. How long did it take to reach its destination $600 \, km$ from the starting point?