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Math Help - equation

  1. #1
    Member GAdams's Avatar
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    equation

    John cycled to school and back.
    The distance to school and back is 20 km.
    On the way to school, John cycled at x km per hour.
    On his way back, Johnís speed decreased by 2 km per hour.
    It took 4 hours altogether to cycle to school and back.

    Write an equation for x.
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  2. #2
    Member GAdams's Avatar
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    I get

    (x + x -2)/2)=20/4

    Doesn't seem right though
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  3. #3
    Moo
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    P(I'm here)=1/3, P(I'm there)=t+1/3
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    Hello,

    Quote Originally Posted by GAdams View Post
    John cycled to school and back.
    The distance to school and back is 20 km.
    On the way to school, John cycled at x km per hour.
    On his way back, Johnís speed decreased by 2 km per hour.
    It took 4 hours altogether to cycle to school and back.

    Write an equation for x.

    10km with speed x km/h.
    10km with speed x-2 km/h.
    The total time was 4 hours.

    Let t_1 be the time he took for going to school, and t_2 be the time to go back.
    We know that t_1+t_2=4 (hours).

    speed=\frac{distance}{time}

    Therefore, x=\frac{10}{t_1} \implies t_1=\frac{10}{x}

    and x-2=\frac{10}{t_2} \implies t_2=\frac{10}{x-2}



    ----> t_1+t_2=4 \implies \frac{\dots}{\dots}+\frac{\dots}{\dots}=4

    Can you take it from here ?
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