.
3 hours and 36 minutes = = = hours.
So, the first pipe fills = of the tank volume per hour.
The two pipes fill of the tank volume per hour, according to the condition.
Hence, the second pipe fills - of the tank volume per hour, which is equal to
- = - = = of the tank volume per hour.
It means that the second pipe will fill the tank in 9 hours.
Answer. It will take exactly 9 hours for the second pipe to fill the tank, working alone.
Any other answer is incorrect.
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It is a typical joint work problem.
There is a wide variety of similar solved joint-work problems with detailed explanations in this site. See the lessons
- Using Fractions to solve word problems on joint work
- Solving more complicated word problems on joint work
- Selected joint-work word problems from the archive
Read them and get be trained in solving joint-work problems.
Also, you have this free of charge online textbook in ALGEBRA-I in this site
- ALGEBRA-I - YOUR ONLINE TEXTBOOK.
The referred lessons are the part of this textbook under the topic
"Rate of work and joint work problems" of the section "Word problems".
Save the link to this online textbook together with its description
Free of charge online textbook in ALGEBRA-I
https://www.algebra.com/algebra/homework/quadratic/lessons/ALGEBRA-I-YOUR-ONLINE-TEXTBOOK.lesson
to your archive and use it when it is needed.
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The lesson to learn from this solution:
If you are given the combined rate of two participants and the rate of one of them, then the rate of the second
participant is the difference of the two given rates.