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1.
A tank can be filled with water by two pipes A and B together in 36 minutes, the tank is filled in 40 minutes. The pipe B can alone fill the tank in -
- A. 45 munutes
- B. 45 munutes
- C. 45 munutes
- D. 45 munutes
Answer: Option D
Explanation:
Let the pipes fill the tank in x minutes.
Part of the tank filled by pipes A and B in one minute: 1/36
Part of the tank filled by pipe A in 1 minute = 1/36−1/x
According to the question,
30 × (1/x) + (1/36−1/x) = 1
⇒30x + 10/9−40/x = 1
⇒10/x = 1/9
Hence, x = 90 minutes.
Part of the tank filled by pipes A and B in one minute: 1/36
Part of the tank filled by pipe A in 1 minute = 1/36−1/x
According to the question,
30 × (1/x) + (1/36−1/x) = 1
⇒30x + 10/9−40/x = 1
⇒10/x = 1/9
Hence, x = 90 minutes.
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