SOLUTION: Hi! I'm having trouble with my Math homework and I'm hoping that you could answer it. Here is the problem: A pipe that takes 30 minutes to fill a tank has been running to fil

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Question 628315: Hi! I'm having trouble with my Math homework and I'm hoping that you could answer it.
Here is the problem:
A pipe that takes 30 minutes to fill a tank has been running to fill an empty tank. After 10 minutes, it is shut off and then a second pipe was opened and was able to fill the tank in 15 minutes. How long will it take the second pipe alone to fill the tank?
Thanks so much!
Answer by ankor@dixie-net.com(22740) (Show Source):
You can put this solution on YOUR website!
A pipe that takes 30 minutes to fill a tank has been running to
fill an empty tank.
After 10 minutes, it is shut off and then a second pipe was opened and was
able to fill the tank in 15 minutes.
How long will it take the second pipe alone to fill the tank?
:
Let x = time for the 2nd pipe to fill the tank alone
Let the completed job = 1, (a full tank)
:
Each pipe will fill a fraction of the tank, the two fractions add up to 1.
:
+ = 1
multiply by 30x, results:
10x + 30(15) = 30x
450 = 30x - 10x
450 = 20x
x =
x = 22.5 minutes the 2nd pipe alone
:
:
Check this
10/20 + 15/22.5 =
1/3 + 2/3 = 1