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gaby236 Group Title

If Jim Roller can paint a room in 3 hours while John Brush would take 5 hours, how long will they take if they work together?

  • one year ago
  • one year ago

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  1. emilie.li Group Title
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    i found this: http://answers.yahoo.com/question/index?qid=20070729140155AAUsPDt

    • one year ago
  2. gaby236 Group Title
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    a;1/8 hour b;8/15 hour c; 7/8 hours

    • one year ago
  3. gaby236 Group Title
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    @RadEn

    • one year ago
  4. wio Group Title
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    What class is this?

    • one year ago
  5. gaby236 Group Title
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    math

    • one year ago
  6. wio Group Title
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    I know, but what level of math?

    • one year ago
  7. gaby236 Group Title
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    i need help

    • one year ago
  8. wio Group Title
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    You need to make a system of equations.

    • one year ago
  9. wio Group Title
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    Let, \(t\) be the time it takes to paint the room. \(r\) is the rate that Roller to paints it, \(b\) is the rate that Brush paints it.

    • one year ago
  10. wio Group Title
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    We know that \[ 3r = 5b \]

    • one year ago
  11. wio Group Title
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    We also know that \[ (r+b)t = 3r = 5b \]

    • one year ago
  12. wio Group Title
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    First solve for \(r\) in terms of \(b\) \[ 3r=5b\implies r = \frac{5}{3}b \]Now plug it into equation 2 \[ \left(\frac{5}{3}b+b\right)t=5b \]

    • one year ago
  13. wio Group Title
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    Then solve for \(t\).

    • one year ago
  14. RadEn Group Title
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    shorcut way : 3*5/(3+5) = 15/8 long way :p v1+v2 = x/3 + x/5 = 8x/15 = x/(15/8) so, if they work together will take 15/8 hours

    • one year ago
  15. RadEn Group Title
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    no correct options there

    • one year ago
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