<PRE><B>Question 309889</B>
Pipes A and B can fill a tank in 45 minutes when used together.
 Alone, pipe A can fill the tank in one hour.
 How long would it take to fill the tank if only pipe B is used?
:
Change 1 hr to 60 min
:
Let b = time for B to fill it alone
:
Let the completed job = 1 (a full tank)
:
{{{45/60}}} + {{{45/b}}} = 1
Reduce the fraction
{{{3/4}}} + {{{45/b}}} = 1
multiply by 4b, results:
3b + 4(45) = 4b
:
3b + 180 = 4b
:
180 = 4b - 3b
:
180 = b
:
B can fill the tank alone in 180 minutes
:
:
Check:
45/60 + 45/180 =
.75 + .25 = 1

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