SOLUTION: 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?

Question 309889: 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?
Found 2 solutions by josmiceli, ankor@dixie-net.com:
Answer by josmiceli(19441) (Show Source): You can put this solution on YOUR website!
You must add their rates of pumping to get the rate
of pumping together
In words, the rate is:
(1 tank)/(time to fill 1 tank)
pipe A:
1 tank/1 hr
pipe B:
1 tank/x hrs
A and B together:

Using pipe B alone, it takes 3 hrs to fill the tank
check:

OK
Answer by ankor@dixie-net.com(22740) (Show Source): You can put this solution on YOUR website!
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)
:
+ = 1
Reduce the fraction
+ = 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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