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Math Help - Maths Help Please

  1. #1
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    Maths Help Please

    Karim occasionally cycles the 24km journey to school. When he hurries and increases his normal average speed, v, by 6km/h his journey time is cut by 40 minutes. How long does it normally take him to cycle to school?
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  2. #2
    Eater of Worlds
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    rt=24

    He increases his speed by 6, (r+6)

    He decreases his time by 2/3 hours, t-2/3

    (r+6)(t-2/3)=24

    But r=24/t

    ((24/t)+6)(t-2/3)=24

    Solve for t.
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  3. #3
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    How do I expand it?

    (6 + (24/t))(t - (2/3)) = 24

    I tried using foil and got the stage:

    6t + 20 .... = 24

    The .... represents -(2/3) * (24/t).

    How do I do that?
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  4. #4
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    Quote Originally Posted by Jehan View Post
    How do I expand it?

    (6 + (24/t))(t - (2/3)) = 24

    I tried using foil and got the stage:

    6t + 20 .... = 24

    The .... represents -(2/3) * (24/t).

    How do I do that?
    Perhaps coding it will make things a bit clearer:
    \left ( 6 + \frac{24}{t} \right ) \left ( t - \frac{2}{3} \right )

    6 \cdot t + 6 \dot -\frac{2}{3} + \frac{24}{t} \cdot t + \frac{24}{t} \cdot - \frac{2}{3}

    Can you see how to do this step now, and can you continue?

    -Dan
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