SOLUTION: I am having trouble with a work/rate word problem. Once my "table" is set up, I think I can do the math, it's setting up the table that's the problem. Two oil pipelines can fil

Question 268605: I am having trouble with a work/rate word problem. Once my "table" is set up, I think I can do the math, it's setting up the table that's the problem.
Two oil pipelines can fill a small tank in 30 minutes. Using one of the pipelines would require 45 minutes to fill the tank. How long would it take the second pipeline alone to fill the tank?
I know my rate is activity divided by time. Would love some help :)
Found 2 solutions by drk, stanbon:
Answer by drk(1908) (Show Source): You can put this solution on YOUR website!
Here is the equation:

step 1 - multiply by 45x to get

step 2 - simplify the left side to get

step 3 - subtract 30x from both sides to get

divide to get

The second pipeline takes 90 minutes alone.
Answer by stanbon(75887) (Show Source): You can put this solution on YOUR website!
Two oil pipelines can fill a small tank in 30 minutes. Using one of the pipelines would require 45 minutes to fill the tank. How long would it take the second pipeline alone to fill the tank?
-------
Together DATA:
time = 30 min/job ; rate = 1/30 job/min
-----
One Pipe DATA:
time = 45 min/job ; rate = 1/45 job/min
--------------
Other pipe DATA:
time = x min/job ; rate = 1/x job/min
------------------------------------------
Equation:
rate + rate = together rate
1/x + 1/45 = 1/30
------------------------
1/x = (1/30)-(1/45)
1/x = 15/(30*45)
15x = 30*45
x = 2*45
x = 90 minutes (time for the "other" pipe to fill the tank)
===============================================================
Cheers,
Stan H.

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