Question

The speed of a boat in still water is $8$ km/hr and speed of the stream is $3$ km/hr. Find time taken by the boat to go $55$ km downstream.

• A. $5$ hrs
• B. $3$ hrs
• C. $2$ hrs
• D. $4$ hrs

Answer 1

The correct option is A $5$ hrs

speed of the boat=$8km/hr$

speed of the stream=$3km/hr$

If the speed of the boat in still water is $xkm/hr$ and speed of the stream is $ykm/hr$ then $speeddownstream=(x+y)km/hr$

Therefore $speeddownstream=8+3=11km/hr$

$distance=55km$

$time=\frac{distance}{speed}$

$\Rightarrow time=\frac{55}{11}$

$\Rightarrow time=5hrs$