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greatuser

  • one year ago

it took 2hrs

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  1. greatuser
    • one year ago
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    it took 2hrs for boat to go from a to b with current and 6hrs to go back against curent. assuming constant speed of boat in both directions, how long wil it take raft (with speed equal to speed of curent) to go from a to b?

  2. hartnn
    • one year ago
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    let the boat (without any current) take 'x' hrs to reach from a to b and the raft (with speed equal to speed of current) take 'y' hrs to reach from a to b when current assist boat, total time taken was 2 hours, so x-y= 2 when current was against the boat, time taken was 6hrs , so x+y =6 find 'y' from here :)

  3. greatuser
    • one year ago
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    that means x=y+2=6-y which means y=2? that cant be right though

  4. hartnn
    • one year ago
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    yeah, i think i have overlooked something speed = distance / time here, distance is same so, speed * time will be constant let their speed be 'a' and 'b' so, (a+b)*2=(a-b)*6=distance =d and you need, time taken by raft, = d/b try it!

  5. greatuser
    • one year ago
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    but d and b are both unknown. how can we solve it?

  6. greatuser
    • one year ago
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    please help i still don't get it

  7. greatuser
    • one year ago
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    so far, a= speed of boat b = sped of current 6a-6b = 2a + 2b meaning a = 2b

  8. dumbcow
    • one year ago
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    "d" is an arbitrary distance that is constant for all trips....let d=1 then 1/(a+b) = 2 1/(a-b) = 6 a = 2b 1/3b = 2 1/b = 6 --> b = 1/6 --> d/b = 6 it would take raft 6 hours

  9. greatuser
    • one year ago
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    oh i get i now thanks a lot

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