$A$ boat moves downstream at the rate of $1 \, km$ in $7 \frac{1}{2} \, \text{minutes}$ and upstream at the rate of $5 \, km/h$. What is the speed (in $km/h$) of the boat in still water?

$A$ man can row $9 \text{ km/hr}$ in still water. If the river is running at $3 \text{ km/hr}$,it takes $3 \text{ hours}$ more to row upstream than to row downstream for the same distance. How far is the place? (in $\text{km}$)

$A$ boat travels $32 \ km$ downstream in $4 \ hours$ and $24 \ km$ upstream in $6 \ hours$. What is the speed (in $km/hr$) of the boat in still water?

$A$ boat goes $2\, km$ upstream and $3\, km$ downstream in $20$ minutes. It goes $7\, km$ upstream and $2\, km$ downstream in $53$ minutes. What is the speed (in $km/hr$) of the boat in still water?

If a boat goes upstream at a speed of $21\, km/h$ and comes back the same distance at $28\, km/h$,what is the average speed (in $km/h$) for the total journey?

$A$ boat travels $60$ km downstream and $20$ km upstream in $4$ hours. The same boat travels $40$ km downstream and $40$ km upstream in $6$ hours. What is the speed (in $km/hr$) of the stream?