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10 April, 19:53

car traveled 576 mi averaging a certain speed. If the car had gone 8 mph faster, the trip would have taken 1 hour less. Find the average speed.

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  1. 10 April, 20:08
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    Answer:64mi/hour

    Step-by-step explanation:

    V=speed * time

    V=s*t ... equation (1)

    v=576

    for taking one hour: t-1

    speed is: s+8

    From equation (1)

    V = (s+8) (t-1)

    (s+8) (t-1) = 576

    Expand the bracket

    st-s+8t-8=576

    Substitute the value of st which is 576

    576-s+8t-8=576

    Collect the like terms

    -s+8t-8=0

    s=8t-8

    Subtitude into the value of s

    576 = (8t-8) * t

    576=8t^2-8t

    8t^2-8t=576

    8t^2-8t-576=0 (divide both by 8)

    t^2-t-72=0

    By factorization method

    Product is (-9 and 8)

    (t-9) (t+8) = 0

    t=9 or t=-8

    V=s*t

    576=s*9

    9s=576

    s=576/9

    s=64mi/hour
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