$A$ swimmer's speed in downstream is $11 \, km/h$ and speed of the stream is $1.5 \, km/h$. Find the upstream speed of the swimmer? (in $km/h$)

$A$ person can row with the stream at $8 \text{ km/h}$ and against the stream at $4 \text{ km/h}$. The speed of the current is (in $\text{km/h}$):

The speed of a boat in still water is $9\, km/h$ and the speed of the stream is $1.5\, km/h$. $A$ man rows to a place at a distance of $105\, km$ and comes back to the starting point. What is the total time taken by him?

$A$ man can row at a speed of $10 \text{ km/h}$ in still water to a certain upstream point and back to the starting point in a river which flows at $4 \text{ km/h}$. Find his average speed for the total journey (in $\text{km/h}$).

The speed of a boat in still water is $10\, km/h$. It covers an upstream distance of $45\, km$ in $6\, h$. The speed (in $km/h$) of the stream is:

$A$ man can row at $5 \text{ km/hr}$ in still water. If the velocity of the current is $1 \text{ km/hr}$ and it takes him $1 \text{ hour}$ to row to a place and come back,how far is the place? (in $\text{km}$)