Question

A person swims downstream 64 km in 4 hours and 40 km upstream in 5 hours. Find his speed in still water and the speed of the stream.

20 km/hr, 12 km/hr

16 km/hr, 8 km/hr

10 km/hr, 2 km/hr

12 km/hr, 4 km/hr


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Answer 1

Answer:

64/4 = 20

40/5 = 8

answer == 16 km/hr, 8 km/hr

Answer 2

Speed in still water= 12 km/hr

Speed of the stream= 4 km/hr

Explanation:

Let x = Speed in still water

y= Speed of the stream.

Then, Speed in downstream =  x+y

Speed in upstream =  x-y

As per given , we have

$\dfrac{64}{x+y}=4$    [∵ $Time=\dfrac{Distance}{speed}$]

$\Rightarrow\ x+y = \dfrac{64}{4}=16\\\\\Rightarrow\ x+y=16------(1)$

Similarly,

$\dfrac{40}{x-y}=5$

$\Rightarrow\ x-y=8------------(2)$

Add (1) and (2) , we get

$2x=24\\\\ x=12$

Put value of x in (1) , we get

$12+y=16\\\\ y=4$

So , Speed in still water= 12 km/hr

Speed of the stream= 4 km/hr

# Learn more :

A person, rowing at the rate of 5 km/h in still water, takes thrice as much time in going 40 km upstream as in going 40 km downstream. Find the speed of the stream. hours. Find the speed of the boat in still water and the speed of the stream.

https://brainly.in/question/1477622