alisha

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a candle is a foot tall after burning an hour. after 4 h it is 10.5 in. tall. write a linear equation to model the height y of the candle after x hours. and how many hours will the candle be 6 inches tall??

plz explain the work .....

  • math -

    plz...help

  • alisha -

    look at it as ordered pairs of the form
    (time, height)
    you are given 2 such points, namely
    (1,12) and (4,10.5)

    slope = (10.5+12)/(4-1)
    = -1.5/3 = -.5 or =1/2

    using height = m(time) + b (remember y=mx+b ?)
    and using the point (1,12)
    we get
    12 = -(1/2)(1) + b
    b = 12.5

    so height = -time/2 + 12.5

    you want height to be 6
    6 = -time/2 + 12.5
    12 = -time + 25
    time = 25-12
    = 13

  • alisha -

    thanks so so so much

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