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algebra

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Dal and kim can assemble a swing set in 1.5 hours. working alone it takes kim 4 hour longer than dal how long will it take dal alone to assemble the swing set

  • algebra -

    dan's rate -- swing/x , where x is the numbers of hours to assemble the swing by himself
    kim's rate --- swing/(x+4)

    so swing/x + swing/(x+4) = swing/1.5
    divide by "swing"
    1/x + 1/(x+4) = 1/1.5
    x+4 + x= (x)(x+4)/1.5
    both sides times 3
    6x+12 = 2x(x+4)
    2x^2 + 2x - 12 = 0
    x^2 + x - 6 = 0
    (x-2)(x+3) = 0
    x = 2 or a negative, which would be silly

    Dal would need 2 hours to do the job himself

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