In one hour, a boat goes $11\text{km}$ along the stream and $5\text{km}$ against the stream. The speed of the boat in still water (in $\text{km/hr}$) is:

Given:
* Downstream speed (along the stream), $u=\frac{11\text{km}}{1\text{hour}}=11\text{km/hr}$
* Upstream speed (against the stream), $v=\frac{5\text{km}}{1\text{hour}}=5\text{km/hr}$

The speed of the boat in still water is given by the formula:

$$\text{Speed in still water}=\frac{u+v}{2}$$

$$\text{Speed in still water}=\frac{11+5}{2}=\frac{16}{2}=8\text{km/hr}$$