<PRE><B>Question 91951</B>
This is working together problem.

The basic idea is, each person finishes part of the job, and together they finish the whole thing which is represented by 100% which is 1.

Jim: 30min    in 1 min Jim can finish  1/30th  of the job

Sue  45min    in 1 min Sue can finish  1/45th  of the job

Tony 90min    in 1 min Tony can finish  1/90th  of the job

Let&#39;s assume it will take them T minutes to finish the job together,

then   {{{T*(1/30 + 1/45 + 1/90) = 1}}}

where {{{1/30 + 1/45 + 1/90}}} represents the portion of the job that can be finished in one minute working together.

Now solve the equation: multiply 90 on both sides

T(3 + 2+ 1) = 90

6T = 90

T = 15 min

So it will take them 15 minutes to fill the pool working together. 

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