Question

A boat goes 6 km against the current of the stream in 2 hours and goes 8 km
along the current in half hour. How long will it take to go 28.5 km in stationary
water?​

Answer 1

Speed of the boatman upstream =

1

2 km/hr = 2 km/hr Speed of the boatman downstream = 6/10/60 km/hr = 6 km/hr

∴ Speed of boatman in stationary water =

2

1 (6+2) km/hr = 4 km/hr

∴ Time taken to cover 5 km in stationary water =

4

5 hrs=1

4

1 hrs = 1 hr 15 min

Answer 2

Answer:

The boat takes 3 hours to travel 28.5km in stationary water.

Explanation:

Given that,

A boat goes 6km against the current of the stream in 2 hours and goes 8km along the current in half hour.We are required to find the time taken by boat to travel 28.5km in still water.

Let the speed of boat in still water be x km/h

and the  speed of current be y km/h

Hence,speed against current is $(x-y)km/h$ and

speed along the current is $(x+y)km/h$

Now according to the given data we have,

$\frac{6}{x-y} =2= > x-y=3-- > (1)$

Similarly,$\frac{8}{x+y} =\frac{1}{2} = > x+y=16-- > (2)$

Solving both the equations,we get x=9.5km/h and y=6.5km/h

Now the time taken by boat to cover 28.5km in stationary water will be

$\frac{28.5}{9.5} =3hr$

Therefore,the boat takes 3 hours to travel 28.5km in stationary water.

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