| A pipe can empty a tank in 40 min. A second pipe with diameter twice as much as that of the first is also attached with the tank to empty it. The two pipes together can empty the tank in |
A) \[8\,\,\min \]
B) \[13\frac{1}{3}\min \]
C) \[30\,\,\min \]
D) \[38\,\,\min \]
Correct Answer: B
Solution :
| First pipe can empty the tank in 40 min. Hence, second pipe has twice the diameter of first pipe, then it can empty tank in half the time, i.e. \[\frac{40}{2}=20\,\,\min .\] |
| \[\therefore \]Part of tank empty in 1 min when both pipe are opened |
| \[=\frac{1}{40}+\frac{1}{20}=\frac{3}{40}\] |
| Hence, two pipes together will empty the tank in |
| \[=\frac{40}{3}=13\frac{1}{3}\min \] |
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