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MATH

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Furnace repairs

A repairman purchased several furnace -blower motors for a total cost of $210. If is cost per motor had been $5 less, he could have purchased one additional motor. How many motors did he buy at the regular rate?

Please help

  • MATH - ,

    regular rate = r
    discount rate = (r-5)
    number bought = n
    number that would have been bought = (n+1)
    so
    210 = r n
    and
    210 = (r-5)(n+1) = r n + r - 5 n -5
    from the first equation r = 210/n
    then the second
    215 = (210/n)n +210/n -5 n
    5 = 210/n -5 n
    5 n = 210 -5 n^2
    n^2 + n - 42 = 0
    (n-8)(n+7)=0
    n = 8

  • sorry factored wrong - ,

    sorry
    (n+7)(n-6) = 0
    n = 6

  • MATH - ,

    check
    r = 210/n = 35
    r-5 = 30
    n+1 = 7
    30 * 7 = 210 check

  • MATH - ,

    thank you very much

  • MATH - ,

    HELP!!!!!I need a better explination.

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