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A boat moves 10 meters/sec relative to the water. If the boat is in a river and the current is 2 meters/ sec, how long will it take the boat to make round trip? it is 1km upstream and 1km down steam. Please explain and show work.

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  1. You need to think of what's going on in the problem.  So on the trip downstream, you're going with the current, so your speed will be faster.  On the trip upstream, you're going against the current, so your speed will be slower.

    Downstream, you're speed is the boat + the river current = 10 + 2 = 12m/s

    Upstream, your speed is the boat - the river current = 10 - 2 = 8 m/s

    Now you want the time, and you have the distance and speed, so use the equation distance / rate = time or D / R = T

    So downstream:  1000 meters / 12 m/s  = 83.33 seconds

    Upstream:  1000 meters / 8 m/s = 125 seconds.  

    Add the times together for the round trip, you get 208.33 seconds.  Got it?

    Hope this helps.


  2. Speed is 12 m/s downstream, 8 m/s upstream

    Trip downstream takes 1000 m / 12 m/s  = 83.3 seconds

    trip upstream takes 1000/8 = 125 seconds

    total time = 208.3 seconds

    .

  3. dont cheat

    1 kilometer = 1000 meters

    so do the math

    if it goes 10 meters in 5 seconds

    how much for 1000

    then calculate round trip

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