<PRE><B>Question 571472</B>
A swimming pool can be filled up by pipes A and B in 3 hours and 35 minutes.
 If pipe A can fill the pool in 6 1/2 hours, how long can pipe B fill it alone?
:
We can do this in minutes, avoid those annoying fractions, then convert the answer back to hrs and min.
3(60) + 35 = 215 min
6(60) + 30 = 390 min
:
Let B = time for pipe B to fill it alone
Let the completed job = 1; (a full pool)
:
A typical shared work equation
{{{215/390}}} + {{{215/B}}} = 1
multiply by 390B
390B*{{{215/390}}} + 390B*{{{215/B}}} = 390B
cancel the denominators and you have
215B + 390(215) = 390B
83850 = 390B - 215B
83850 = 175B
B = {{{83850/175}}}
B = 479.143 minutes
:
Convert to hrs and min, divide by 60; mult the decimal portion times 60
7 + .986(60) = 7 hrs 59 minutes for B to the job
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