SOLUTION: Frank can build a fence in twice the time it would take Sandy. Working together, they can build it in 7 hrs. How long will it take each if them to do it alone?

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Question 1044056: Frank can build a fence in twice the time it would take Sandy. Working together, they can build it in 7 hrs. How long will it take each if them to do it alone?
Answer by ikleyn(52905) About Me  (Show Source):
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Frank can build a fence in twice the time it would take Sandy. Working together, they can build it in 7 hrs.
How long will it take each if them to do it alone?
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1%2FF+%2B+1%2FS = 1%2F7,        (1)
F = 2S.            (2)

--->

1%2FF+%2B+1%2F%282F%29 = 1%2F7,  --->  3%2F%282F%29 = 1%2F7  --->  F = %283%2A7%29%2F2 = 21%2F2 = 101%2F2 hours is the time for Frank.

Then the time for Sandy is 21%2F4 = 51%2F4 hours.

Answer.  101%2F2 hours is the time for Frank;  21%2F4 = 51%2F4 hours is the time for Sandy.

For details on how to solve joint work problems see the lesson
    - Using Fractions to solve word problems on joint work,
in this site.