Math

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Mike can mow a lawn in 3 hours. Paul can mow the same lawn in 2 hours. How long would it take both of them working together to mow the lawn? The answer is suppose to be 20/9.

This is what I did and I get 9/20. What am i doing wrong?
1.4x+1/5x=1 which gives u 9/20. I'm so lost...

  • Math -

    Mike's rate = 1/3 lawn/hr
    Paul's rate = 1/2 lawn/h

    combined rate = (1/3 + 1/2) lawn/hr
    = 5/6 lawn/hr

    time for combined rate = 1/(5/6) hours
    = 6/5 hours

    Their answer is wrong.
    How can it take 20/9 or more than 2 hours for both of them to do it, when Paul alone could do it in 2 hours.

  • Math -

    6/5hrs

  • Math -

    t = 3*2 / (3+2) = 6/5 hrs.

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