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anonymous

  • 5 years ago

Help plz, Set up an equation to solve the following problem, and then solve it. On a sales trip, Irwin drove 330 miles averaging a certain speed. The return trip was at an average speed that is 11mph faster. Total time for the round trip was 11 hours. Find Irwin’s average speed on each part of the trip.

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  1. anonymous
    • 5 years ago
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    well, its not hard , what dont we know , what we do we need to find , assign them to variables

  2. radar
    • 5 years ago
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    Use distance equal rate times time.

  3. anonymous
    • 5 years ago
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    let x equal the "certain speed"

  4. anonymous
    • 5 years ago
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    so assume 330 miles for one way , that means in total he drove 660miles

  5. anonymous
    • 5 years ago
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    we know the total time was 11 but time = distance / speed time for first section = 330 / x times for second section = 330/ ( x+11) so ( 330/x) + [330 / (x+11) = 11

  6. anonymous
    • 5 years ago
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    \[\frac{330}{x} + \frac{330}{x+11} =11\]

  7. anonymous
    • 5 years ago
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    solve for x

  8. anonymous
    • 5 years ago
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    i c. Thanks

  9. anonymous
    • 5 years ago
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    it has two solutions x=-6, x=55 but because we are dealling with real world ( and yes, it says "speed", not velocity ) so a negative value is not allowed

  10. anonymous
    • 5 years ago
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    so x=55 means for first half average was 55mph, and for second half average was 66mph ( ie 55 +11 )

  11. radar
    • 5 years ago
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    Actually the average speed for the entire trip was 660/11 or 60 mi. So wouldn't that made the avg speed for the first part 54.5 mph and the second part 65.5?

  12. anonymous
    • 5 years ago
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    dnt think so

  13. radar
    • 5 years ago
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    The avg of 54.5 + 65.5 is 120/2=60

  14. anonymous
    • 5 years ago
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    firstly where did u magically get 54.5 and 65.5 from

  15. radar
    • 5 years ago
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    x + (x+11) 660 ---------- = ----- = 60 2 11

  16. radar
    • 5 years ago
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    Nothing magic about it.

  17. anonymous
    • 5 years ago
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    yes.... and.....?

  18. anonymous
    • 5 years ago
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    yes there is , there are alot of different ways to get two numbers to sum to 120 , why did you pick those two numbers? , theres no calculations to suggest why you chose thoise two

  19. anonymous
    • 5 years ago
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    ohh I think i see what you are doing now

  20. anonymous
    • 5 years ago
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    bit of a dangerous way to think

  21. radar
    • 5 years ago
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    x= first avg speed (certain speed) x+11 is the second avg speed (return trip Their sum divided by 2 equals the total avg speed 660/11 is also the total avg speed. Take it from there

  22. radar
    • 5 years ago
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    Just sayin your way seems correct just wondering why they dont come out the same. Did you round off or take a root of or whatever/

  23. anonymous
    • 5 years ago
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    no, the reason why they dont come out correct is because your way of thinking is wrong :P

  24. radar
    • 5 years ago
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    Well they came out close.lol gotta run

  25. anonymous
    • 5 years ago
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    :\, the average of a sum is not the sum of the avergaes

  26. radar
    • 5 years ago
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    Gotcha, I see the error of my logic.

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