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A boat travels 2km upstream and 2km downstream. The total time for both parts of the trip is 1 hour. The spee of the stream is 2km per hour. What is the speed of the boat in still water?

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Answer #1

I think the answer is 2srt2 which is 4.828427124746 thanks

Answer #2

using b1ff’s method, I got 4.828427124746km/h as a pretty accurate estimate :)

Answer #3

it is hard .,, can you show me the answer ?

Answer #4

what ?

Answer #5

4km/hr

Answer #6

You know the two legs of the trip take 1 hours total, so T1+T2 = 1hour.

You know the distance of each leg is 2 km, and distance is speed times time.

s=vt.

So s/v =t

Therefore you can say:

s/(v-vs) + s/(v+vs) = 1

Where vs is stream speed.

You cross multiply this or any method you like, and factorise it, so get a solution of around 4.8km/hour (ignore the negative value).

Checking 4.8km/hour:

It would take t=s/v T1=2/2.8 = 5/7

T2 = 2/6.8 = 5/17

Add them up, and you get 120/119 = 1.008 hours.

So pretty close, just find the solution of the factor more accurately than I did.

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