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How fast does light travel from sun to Saturn equation

  1. Jun 12, 2014 #1
    1. the distance between the sun and Saturn is approx. 8.9x10^8 mi. The speed of light is approx. 1.9x10^5 miles per second.
    How long does it take light to travel from the sun to Saturn?
    Answer in units of seconds.

    2. Relevant equations

    3. The attempt at a solution
    I have tried multiplying the two, dividing the two, and adding the two, and converting. I am utterly lost, and would appreciate any help anyone could offer! :)
  2. jcsd
  3. Jun 12, 2014 #2


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    Homework Helper

    Time * Speed = Distance


    Time = ?

    I don't advise trying to get the answer randomly (by random, I mean, without logic)

    There are simply wayyy toooo many options that it is very unlikely you will find the answer that way
    (and what about when you don't have an answer sheet?)
  4. Jun 12, 2014 #3
    Ok, so assuming I kinda understand now, would I set up the equation like T x 1.9x10^5miles/sec = 8.9x10^8 miles? Then divide the speed and the distance to get time?
  5. Jun 12, 2014 #4


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    Staff Emeritus
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    It's like this: I'm 10 miles from town. I'm walking at 2 miles per hour. How many hours will it take me to walk 10 miles?
  6. Jun 13, 2014 #5


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    Staff: Mentor

    Your equation is correct. Your idea of dividing them is a correct one as well, but it is not clear where you got it from, so it is hard to tell if you found it in some systematic way (always preferred) or just by randomly juggling (which occasionally gives correct results).

    Please elaborate on why you did it this way.
  7. Jun 13, 2014 #6


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    When you have no idea how to proceed, one thing to try is to look at the units of the things you know and the thing you are looking for. There will often be only one way to combine the things you know to get what you are looking for. Here, you know the speed (L/T), and the distance (L), and you are looking for the time (T) (with L being length and T being time, in whatever system of units you are using). How can you combine L/T and L in order to end up with T?
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