Question

The time taken by a boat to go a certain distance against the current is the same as to go the double distance


along the current. The speed of the current is 3 km/h. How much time in hours) will the boat take to travel
57.6 km in still water?​

Answer 1

Answer:

Let distance be x km

Speed downstream = 5+2 = 7 km /hr.

Speed upstream = 5-2 = 3 km/hr.

So 3x−7x=2

7x−3x=2×21

4x = 42

x=42/4

x=10.5 km/h

Answer 2

Answer:

6.4

Step-by-step explanation:

let u=speed of the boat in still water

v=speed of the stream/current

According to the question,

$\frac{d}{u - v} = \frac{2d}{u + v}$

given speed of the current=3km/hr

so,

$\frac{d}{u - 3} = \frac{2d}{u + 3}$

$u + 3 = 2u - 6$

u=9

given distance=57.6km

so time taken to travel in still water=57.6/9

t=6.4hr