$A$ man's speed with the current is $15 \, km/hr$,and the speed of the current is $2.5 \, km/hr$. The man's speed against the current is.......$km/hr$

$A$ man can row $15\, km/h$ downstream and $9\, km/h$ upstream. The speed of the boat in still water is.....$km/h$

$A$ man can row at the rate of $4 \text{ km/hr}$ in still water. If the time taken to row a certain distance upstream is $3$ times as much as to row the same distance downstream,find the speed of the current in $\text{km/hr}$.

$A$ man swimming in a stream which flows at $1.5 \, km/hr$ finds that in a given time he can swim twice as far with the stream as he can against it. At what rate does he swim in still water? (in $km/hr$)

$A$ man can row upstream $36 \text{ km}$ in $6 \text{ hours}$. If the speed of a man in still water is $8 \text{ km/hr}$,find how much distance he can cover downstream in $10 \text{ hours}$? (in $\text{km}$)

$A$ man can row against the current $3/4$ of a kilometre in $15$ $min$ and returns the same distance in $10$ $min.$ The ratio of his speed to that of the current is: