Question

A boat goes 8 km in one hour along the stream and 2 km in one hour against the stream. The speed in km/hr of the stream is

Answer 1

Answer:

A boat can travel with a speed of 15 km/hr in still water. If the speed of the stream is 6 km/hr, what is the time taken by the boat to go 69 km downstream? A boat goes 30 km upstream and 44 km downstream in 10 hours. In 13 hours, it can go 40 km upstream and 55 km down-stream.

Answer 2

Answer:

3 km/h

Explanation:

Let x be the speed of the boat and y be the speed of the stream, ( both are in km/h )

∵ speed of boat in downstream = speed of boat + speed of stream

= (x+y) km/h

And, the speed of boat in upstream = speed of boat - speed of stream

= (x-y) km/h,

Now, the covered distance in down stream = 8 km,

So, time taken in down stream = $\frac{Distance}{speed}$

$=\frac{8}{x+y}$

Similarly, the covered distance in upstream = 2 km,

So, time taken = $\frac{2}{x-y}$

According to the question,

$\frac{8}{x+y}=1\text{ and }\frac{2}{x-y}=1$

⇒ x + y = 8 ----(1),

And, x - y = 2 ----(2),

Equation (1) - equation (2),

2y = 6

⇒ y = 3

Hence, the speed of the stream = 3 km/h.