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Math Help - Estimating Speed of a Vehicle

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    Estimating Speed of a Vehicle

    The speed a vehicle was traveling, s, in miles per hour, when the brakes were first applied, can be estimated using the formula:


    Estimating Speed of a Vehicle-003.jpg


    where d is the length of the vehicle's skid marks, in feet.

    a) Determine the speed of a car that made skid marks 4ft long.

    b) Determine the speed of a car that made skid marks 16ft long.

    c) Determine the speed of a car that made skid marks 256ft. long.
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    Quote Originally Posted by camstill View Post
    The speed a vehicle was traveling, s, in miles per hour, when the brakes were first applied, can be estimated using the formula:


    Click image for larger version. 

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    where d is the length of the vehicle's skid marks, in feet.

    a) Determine the speed of a car that made skid marks 4ft long.

    b) Determine the speed of a car that made skid marks 16ft long.

    c) Determine the speed of a car that made skid marks 256ft. long.
    Well then, these look like plug and chug kind of problems. They are all done the same way. Here's the first one.

    s=\sqrt{\frac{d}{0.04}}

    s=\sqrt{\frac{4}{0.04}}

    s=\sqrt{100}

    s=10 miles/hr
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    Thanks, but...........

    I can't figure out the 2nd step to get to the 3rd step? Can you elaborate? Thank you!
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    Quote Originally Posted by camstill View Post
    I can't figure out the 2nd step to get to the 3rd step? Can you elaborate? Thank you!
    In the second step, after I substituted 4 for d, I divided 4 by .04.

    4 \div .04=4 \div \frac{4}{100}=\frac{4}{1} \times \frac{100}{4}=\frac{400}{4}=100
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    Silly me......

    I was forgeting the radical sign. Thank you so much for the help!
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