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Math Help - unit problem

  1. #1
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    unit problem

    Car costs $14,500 and has a rated mileage of 28 miles/gallon. another car costs $21,700 and has a rated mileage of 19 kilometers/liter. the cost of gasoline is $1.25/gal. How many miles do you have to drive for the lower fuel consumption of the second car to compensate for the higher cost of this car?
    thanks a lot
    it's driving me crazy
    nertil
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  2. #2
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    Quote Originally Posted by nertil1 View Post
    Car costs $14,500 and has a rated mileage of 28 miles/gallon. another car costs $21,700 and has a rated mileage of 19 kilometers/liter. the cost of gasoline is $1.25/gal. How many miles do you have to drive for the lower fuel consumption of the second car to compensate for the higher cost of this car?
    thanks a lot
    it's driving me crazy
    nertil
    I'll tell you, but first you have to tell me what 19 kilos per liter are in miles per gallon.
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  3. #3
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    44.7 mi/gal
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  4. #4
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    Quote Originally Posted by nertil1 View Post
    44.7 mi/gal
    Quote Originally Posted by nertil1 View Post
    Car costs $14,500 and has a rated mileage of 28 miles/gallon. another car costs $21,700 and has a rated mileage of 19 kilometers/liter. the cost of gasoline is $1.25/gal. How many miles do you have to drive for the lower fuel consumption of the second car to compensate for the higher cost of this car?
    thanks a lot
    it's driving me crazy
    nertil
    Ok then.

    What you need to do is write a function to compare the amount of miles gone ( x) to the amount of money paid ( y) for both cars.

    For the first car, you would spend \frac{1_{\text{gallon}}}{28_{\text{miles}}}\times\  frac{\$ 1.25}{1_{\text{gallon}}}=\frac{\$ 1.25}{28_{\text{miles}}}=\frac{\$ 5}{112_{\text{miles}}}

    or just 5 dollars for every 112 miles

    So the equation for the cost of the first car is: y=\frac{5}{112}x+14500

    Now your job is to find the equation of the second car. And then see when they intersect...
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  5. #5
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    Quote Originally Posted by nertil1 View Post
    where did 5/122 come from?
    it's 1.25/28

    that's the smallest fraction it could be without having a decimal place (I hate decimal places in fractions)
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