Question:
A pipe 'P' can fill a tank in 20 hours and another pipe 'Q' in 30 hours. If both pipes are opened in an empty tank, how much time will they take to fill it?
A pipe 'P' can fill a tank in 20 hours and another pipe 'Q' in 30 hours. If both pipes are opened in an empty tank, how much time will they take to fill it?
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Total time = $\frac{xy}{x+y} = \frac{20 \times 30}{20 + 30}$.
Updated On: Jun 26, 2026
- 12 hours
- 15 hours
- 20 hours
- 50 hours
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Verified By Collegedunia
The Correct Option is A
Solution and Explanation
Step 1: Concept
Time and Work (Pipes and Cisterns).
Step 2: Analysis
Rate of P = $1/20$ per hour. Rate of Q = $1/30$ per hour.
Step 3: Calculation
Combined rate = $\frac{1}{20} + \frac{1}{30} = \frac{3+2}{60} = \frac{5}{60} = \frac{1}{12}$.
Time taken = 12 hours.
Step 4: Conclusion
Both pipes together will fill the tank in 12 hours. Final Answer: (A)
Time and Work (Pipes and Cisterns).
Step 2: Analysis
Rate of P = $1/20$ per hour. Rate of Q = $1/30$ per hour.
Step 3: Calculation
Combined rate = $\frac{1}{20} + \frac{1}{30} = \frac{3+2}{60} = \frac{5}{60} = \frac{1}{12}$.
Time taken = 12 hours.
Step 4: Conclusion
Both pipes together will fill the tank in 12 hours. Final Answer: (A)
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