Pipe A can fill a tank in 20 minutes and pipe B can fill the same tank in 30 minutes. If pipe A is opened and 8 minutes later pipe B is also opened, then in how many minutes will the tank be full?
Correct Answer: Description for Correct answer:
Pipe A is opened for 8min.
Therefore, it will fill \( \Large \frac{8}{20} \)th of the tank. (That is, \( \Large \frac{2}{5} \) of the tank)
Remaining \( \Large \frac{3}{5} \)th of the tank has to be filled by A and B together.
A and B can together fill \( \Large \left(\frac{1}{20}+\frac{1}{30}\right)=\frac{1}{12} \)th of the tank in a minute.
Remaining tank will get filled in \( \Large \frac{3}{5} \times 12=\frac{36}{5} \) = 7.2 min
Therefore, total tank will be filled in 8 + 7.2 = 15.2 min
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