Question

A streamer moves with velocity 3km/h against the direction of river water whose velocity is 2 km/h. The total time taken for the journey if the boat travel 3 km in direction of the stream and then back to its place is?

Answer 1

Velocity of streamer = 3 km/hr
Velocity of river = 2 km/hr
Total distance travelled = 3 km upstream + 3 km downstream
Total distance = 6 km
Streamer travels 3 km in the direction of the river.
Effective velocity of streamer = 3 + 2 = 5 km/hr
$Timetaken=\frac{distance}{velocity}=\frac{3km}{5km/hr}$
$Timetaken=T_1=\frac{3}{5}hrs$
Streamer travels 3 km back (against the river)
Effective velocity = 3 km/hr = 2 km/hr
=1 km/hr
$Timetaken\left(T_2\right)=\frac{Distance}{Time}=\frac{3}{1}$
$\therefore$ Time taken = $T_2$ = 3 hours
Total time taken = $\frac{3}{5}+3=\frac{18}{5}hours$
= 3.6 hours
= 3 hours 36 mins.