The distance between Point $X$and Point $Y$ is $80$ $\mathrm{km}$. Boat A could travel from Point $X$ to $Y$ upstream and Point $Y$ to $X$ downstream in total of $30$ $\mathrm{hours}$. Boat B could travel from Point $X$ to $Y$ upstream and Point $Y$ to $X$ downstream in a total of $9$ $\mathrm{hours}$. If the speed of boat B in still water is thrice of boat A in still water, what is the speed of Boat B? (Please note: speed of the current is constant for both):

The downstream speed of a boat is $42$ km/hr and the speed of current is $3$ km/hr. What is the total time (in hours) taken by the boat to cover $72$ km upstream and $84$ km downstream?

A boat in still water takes $15$ hours to reach its destination and come back from there. In the same river, it takes $16$ hours for the same journey where there is a current in the water. The difference between the speed of the boat and the river current is $15$ $km/hr$. Find out the speed of the river?

Ratio between speed of boat in still water to speed of stream is $8:1$.If $67.5$ kms is travelled downstream in $2.5$ hours then find the difference between speed of boat in still water to speed of stream?

Quantity $1$: Ratio between the speed of the boat in still water to the speed of the stream is $2:1$. Total time taken by a man to cover distance of $72$ km in upstream and comeback is $32$ hours. Find downstream speed.

Quantity $2$: $9$ $9 \mathrm{km}/\mathrm{h}$.

The speed of a stream is $3 \mathrm{km}/\mathrm{hr}$. A boat goes $60 \mathrm{km}$ and comes back to the starting point in $15$ hours. What is the speed (in $\mathrm{km}/\mathrm{hr}$) of the boat in still water?

Speed of a boat along with the current and against the current are $12$ km/hr and $6$ km/hr respectively. What is the speed of the boat (in km/hr) in still water?