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  1. #1
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    help!

    "1. A train travels 35 miles per hour for 170 minutes
    How far will the train travel in this time?

    A car completed this same journey in 60% of the time the train took
    Find the average speed of the car in mph

    2. Y is inversely proportional to X. When Y=4, X=3.
    Find an equation linking X and Y.

    If X = 6 find the value of Y. (Hint, use the equation you've found above)"

    there's no words to explain how confused i am right now
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  2. #2
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    Quote Originally Posted by amy15 View Post
    2. Y is inversely proportional to X. When Y=4, X=3.
    Find an equation linking X and Y.

    If X = 6 find the value of Y. (Hint, use the equation you've found above)"

    there's no words to explain how confused i am right now
    "Y is inversely proportional to X"
    $\displaystyle -\,\, Y = \frac{k}{X^2}$

    "When Y=4, X=3"
    $\displaystyle -\,\, 4 = \frac{k}{3^2} \Rightarrow k = 36$

    "Find an equation linking X and Y."
    $\displaystyle -\,\, Y = \frac{36}{X^2}$

    "If X = 6 find the value of Y. (Hint, use the equation you've found above)"
    $\displaystyle -\,\, Y = \frac{36}{6^2}\Rightarrow Y = 1$

    "there's no words to explain how confused i am right now "
    $\displaystyle -\,\,\text{Oops....At least, I hope you are not now}$
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  3. #3
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    thanks! i'm not so confused anymore
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  4. #4
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    Question 1

    1: $\displaystyle \text{distance}=\text{speed}\times\text{time}$

    In this case, the speed is 35 mph, and the time is 170 minutes ($\displaystyle {170}\div{60}$ hours)

    so the distance that the train travels is $\displaystyle 35\times (170\div60)= 99.167$ miles.

    The car traveled 99.167 miles in 60% of 170 minutes.
    So it travelled 99.167 miles in $\displaystyle \frac{170}{100}\times60=102$ minutes ($\displaystyle 102\div60=1.7$ hours)

    $\displaystyle \text{speed}=\frac{\text{distance}}{\text{time}}$

    Therefore the average speed is $\displaystyle \frac{99.167}{1.7}=58.334$ mph
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