A boat travel $$240 \mathrm{~km}$$ downstream in 3 hours and the time is taken by the boat to travel the same distance in upstream in 6 hours. Find the speed of stream (in kmph).

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A boat travel $$240 \mathrm{~km}$$ downstream in 3 hours and the time is taken by the boat to travel the same distance in upstream in 6 hours. Find the speed of stream (in kmph).

The time is taken by the boat to cover upstream distance $$=6$$ hours

Formula used:
Upstream speed $$=u-v$$
Downstream speed $$=u+v$$
Where,
$$\mathrm{u}$$, is the speed of the boat
$$v$$, is the speed of the stream
Speed $$=\frac{\text { Distance }}{\text { Time }}$$

Calculation:
The upstream speed,
\begin{aligned} &\Rightarrow \mathrm{u}-\mathrm{v}=\frac{240}{6} \\ &\Rightarrow \mathrm{u}-\mathrm{v}=40 \mathrm{kmph} \quad-(1) \end{aligned}
The downstream speed,
\begin{aligned} &\Rightarrow \mathrm{u}+\mathrm{v}=\frac{240}{3} \\ &\Rightarrow \mathrm{u}+\mathrm{v}=80 \mathrm{kmph} \quad-(2) \end{aligned}
On subtracting the equation (1) from equation (2), we get,
\begin{aligned} &\Rightarrow 2 \mathrm{v}=40 \\ &\Rightarrow \mathrm{v}=20 \mathrm{kmph} \end{aligned}

The speed of the stream $$=20 \mathrm{kmph}$$

$$\therefore$$ The speed of the stream is $$20 \mathrm{kmph}$$.