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Math Help - Problem on hw

  1. #1
    Junior Member
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    Problem on hw

    Sam can do a job in 4 days
    Lisa can do a job in 6 days
    Tom can do a job in 2 days

    How long can Sam Lisa and Tom complete the job?

    .8 1.09 1.23 1.65 1.97

    I cannot remember how to start this problem can somebody please help me
    Thank you
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  2. #2
    MHF Contributor Quick's Avatar
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    Quote Originally Posted by schinb64 View Post
    Sam can do a job in 4 days
    Lisa can do a job in 6 days
    Tom can do a job in 2 days

    How long can Sam Lisa and Tom complete the job?

    .8 1.09 1.23 1.65 1.97

    I cannot remember how to start this problem can somebody please help me
    Thank you
    hmm...

    Sam does 1/4 of a job per day (job per day is like miles per hour, if you want to think of it that way)

    Lisa has a speed of 1/6 of a job per day

    Tom has a speed of 1/2 of a job per day

    So, they complete the job n amount of days later...

    \frac{1}{4}n+\frac{1}{6}n+\frac{1}{2}n=1

    Let's solve for n, first we multiply both sides by 12 to get:

    3n+2n+6n=12

    Then add:

    11n=12

    Then divide:

    n=\frac{12}{11}=1.0909090909090909090909...

    So they can finish the job in \approx 1.09 \text{ days}
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