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Math Help - Quadratic help!!

  1. #1
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    Red face Quadratic help!!

    marnie can walk 1km/m faster the jon. She completes a 20km hike 1 hour before him. Write an equation and solve it to find there walking speeds.

    i cannot seem to solve this ahh plz help me
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  2. #2
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    Hello LaylaSam
    Quote Originally Posted by LaylaSam View Post
    marnie can walk 1km/m faster the jon. She completes a 20km hike 1 hour before him. Write an equation and solve it to find there walking speeds.

    i cannot seem to solve this ahh plz help me
    Suppose that Jon walks at x kph. Then Marnie walks at x+1 kph.

    Using the formula
    \text{time} = \dfrac{\text{distance}}{\text{speed}}
    Marnie takes \frac{20}{x+1} hours, and Jon takes \frac{20}{x} hours.

    Since Jon takes 1 hour more than Marnie, we get:
    \dfrac{20}{x}=\dfrac{20}{x+1}+1
    Now multiply both sides by x(x+1) to get rid of fractions:
    20(x+1)=20x+x(x+1)

    \Rightarrow 20x+20=20x+x^2+x

    \Rightarrow x^2+x-20=0

    \Rightarrow (x+5)(x-4)=0

    \Rightarrow x = 4, since x=-5 is impossible.

    So Jon walks at 4 kph and Marnie at 5 kph.

    Grandad
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  3. #3
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    Omg ur a genious!!!
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