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Homework Help: A question about boats

  1. Sep 18, 2015 #1
    1. The problem statement, all variables and given/known data
    Two boats start together and race across a 70-km-wide lake and back. Boat A goes across at 70 km/h and returns at 70 km/h. Boat B goes across at 35 km/h, and its crew, realizing how far behind it is getting, returns at 105 km/h. Turnaround times are negligible, and the boat that completes the round trip first wins.

    Boat A wins but by how much?

    3. The attempt at a solution

    So I entered into a velocity calculator to determine that it would take Boat A 2hours to finish the course while it would take Boat B 2hrs 40 min to complete the course or simply put boat A wins by 40min

    70kmh at 40 minutes would travel 46.667km and yet when I enter the answer for my online homework thingy it says it wrong even when I enter it as 46, 46.6,46.66, and 46.667

    What am I missing hear?
  2. jcsd
  3. Sep 18, 2015 #2


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    Staff Emeritus
    Science Advisor
    Homework Helper

    Well, you are not rounding 46.666666... correctly, for one thing. Instead of rounding, you are truncating the decimal by chopping off the extra digits.

    46.6666.... would be either 46.67, 46.7, or just 47, depending on how many sig figs you wish to carry.
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