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Math Help - Problem involving work

  1. #1
    Newbie
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    Feb 2009
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    Problem involving work

    I think I figured it out but here is the problem
    One person can do a task in 10hrs, a second can do it in 15 and the third can do it in 20. Together how long will it tak
    so here is what I came up with
    x/10+x/15+x/20=1
    60(x/10+x/15+x/20)=1*60
    6x+4x+3x=60
    13x=60
    13x/13=60/13
    x=4.62
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  2. #2
    Junior Member
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    Nov 2008
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    It's right.
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  3. #3
    Super Member

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    Lexington, MA (USA)
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    Hello, roachbeats!

    I think I figured it out

    One person can do a task in 10 hrs, a second in 15 hours, and a third in 20 hours.
    Together, how long will it take?

    So here is what I came up with: . \frac{x}{10}+\frac{x}{15}+\frac{x}{20} \:=\:1

    . . 60\left(\frac{x}{10}+\frac{x}{15}+\frac{x}{20}\rig  ht)\:=\:1\cdot60

    . . 6x+4x+3x\:=\:60 \quad\Rightarrow\quad 13x\:=\:60 \quad\Rightarrow\quad x\:=\:\frac{60}{13} \:\approx\:4.62\text{ hrs}

    Absolutely correct! . . . Lovely work!

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