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Time and Work
Pipes and Cisterns
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RRB NTPC Graduate Tier 1 2025 Shift-3 📅 06 Jun, 2025

Pipe A can fill a tank in 9 minutes, while pipe B can empty the completely filled tank in 10 minutes. Initially, pipe A is opened and after 3 minutes pipe B is also opened. In how much time (in minutes) will the remaining tank be filled completely?

A
47
B
60
C
73
D
61
Result Summary
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RRB NTPC Graduate Tier 1
2025 • 06 Jun, 2025 • Shift-3
Pipe A can fill a tank in 9 minutes, while pipe B can empty the completely filled tank in 10 minutes. Initially, pipe A is opened and after 3 minutes pipe B is also opened. In how much time (in minutes) will the remaining tank be filled completely?
Correct Answer
60
Initial Work Analysis: Pipe A fills at a rate of 1/9 of the tank per minute. In the first 3 minutes, Pipe A fills $3 \times (1/9) = 1/3$ of the tank.Remaining W......
Ref/Book : RRB NTPC Graduate Tier 1 2025
Ref. Subject Time and Work
Chapter -
Ref. Topic Pipes and Cisterns
Pg. No -
💡 Analysis & Explanation
Initial Work Analysis ▼
Pipe A fills at a rate of 1/9 of the tank per minute. In the first 3 minutes, Pipe A fills $3 \times (1/9) = 1/3$ of the tank.
Remaining Work Assessment ▼
After 3 minutes, $1 - 1/3 = 2/3$ of the tank remains to be filled.
Combined Rate Calculation ▼
When both pipes are open, the net filling rate is $(1/9) - (1/10) = (10 - 9) / 90 = 1/90$ of the tank per minute.
Time for Remaining Task ▼
To fill the remaining 2/3 of the tank at a rate of 1/90 per minute, the time required is $(2/3) / (1/90) = (2/3) \times 90 = 60$ minutes.
Conclusion ▼
It will take 60 minutes to fill the remaining portion of the tank.
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