Question 852930
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If two water pipes can fill a swimming pool in 18 hours when both are open. One of the pipes can fill the pool alone in 45 hours , how long would it take the other pipe to fill the pool alone?
Ans:
Pipe A fills 1/45 of the pool per hour.
Let pipe B take x hours to fill the pool. So in one hour, it fills 1/x of the pool.
So in one hour, they together fill 1/x + 1/45 = {{{(x + 45)/(45*x)}}} of the pool.
In 18 hours, they fill 100% of the pool. So the  equation is:
{{{18*(x + 45)/(45*x) = 1}}}
or
{{{18*(x + 45) = 45*x}}}
or
{{{810 = 27*x}}} or {{{x = 30}}}

So the pipe B would take 30 hours to fill the pool by itself.

Hope this helps.
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