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

Algebra ->  Rate-of-work-word-problems -> 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      Log On


   



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) About Me  (Show Source):
You can put this solution on YOUR website!
Here is the equation:
%281%2F45%29%2A30+%2B+%281%2Fx%29%2A30+=+1
step 1 - multiply by 45x to get
30x+%2B+30%2A45+=+45x
step 2 - simplify the left side to get
1350+%2B+30x+=+45x
step 3 - subtract 30x from both sides to get
1350+=+15x
divide to get
x+=+90
The second pipeline takes 90 minutes alone.

Answer by stanbon(75887) About Me  (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.