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Home Aptitude Pipes and Cistern Comments

  • Question
  • Two pipes A and B together can fill a cistern in 4 hours. Had they been opened separately, then B would have taken 6 hours more than A to fill the cistern. How much time will be taken by A to fill the cistern separately?


  • Options
  • A. 1 hour
  • B. 2 hours
  • C. 6 hours
  • D. 8 hours

  • Correct Answer
  • 6 hours 

    Explanation
    Let the cistern be filled by pipe A alone in x hours.

    Then, pipe B will fill it in (x + 6) hours.

    1 + 1 = 1
    x (x + 6) 4

    x + 6 + x = 1
    x(x + 6) 4

    x2 - 2x - 24 = 0

    ⟹ (x -6)(x + 4) = 0

    x = 6.     [neglecting the negative value of x]


    Pipes and Cistern problems


    Search Results


    • 1. A tank is filled in 5 hours by three pipes A, B and C. The pipe C is twice as fast as B and B is twice as fast as A. How much time will pipe A alone take to fill the tank?

    • Options
    • A. 20 hours
    • B. 25 hours
    • C. 35 hours
    • D. Cannot be determined
    • E. None of these
    • Discuss
    • 2. Two number are in the ratio 3 : 5. If 9 is subtracted from each, the new numbers are in the ratio 12 : 23. The smaller number is:

    • Options
    • A. 27
    • B. 33
    • C. 49
    • D. 55
    • Discuss
    • 3. If 0.75 : x :: 5 : 8, then x is equal to:

    • Options
    • A. 1.12
    • B. 1.2
    • C. 1.25
    • D. 1.30
    • Discuss
    • 4. In a mixture 60 litres, the ratio of milk and water 2 : 1. If this ratio is to be 1 : 2, then the quanity of water to be further added is:

    • Options
    • A. 20 litres
    • B. 30 litres
    • C. 40 litres
    • D. 60 litres
    • Discuss
    • 5. The salaries A, B, C are in the ratio 2 : 3 : 5. If the increments of 15%, 10% and 20% are allowed respectively in their salaries, then what will be new ratio of their salaries?

    • Options
    • A. 3 : 3 : 10
    • B. 10 : 11 : 20
    • C. 23 : 33 : 60
    • D. Cannot be determined
    • Discuss
    • 6. Three pipes A, B and C can fill a tank in 6 hours. After working at it together for 2 hours, C is closed and A and B can fill the remaining part in 7 hours. The number of hours taken by C alone to fill the tank is:

    • Options
    • A. 10
    • B. 12
    • C. 14
    • D. 16
    • Discuss
    • 7. A tank is filled by three pipes with uniform flow. The first two pipes operating simultaneously fill the tank in the same time during which the tank is filled by the third pipe alone. The second pipe fills the tank 5 hours faster than the first pipe and 4 hours slower than the third pipe. The time required by the first pipe is:

    • Options
    • A. 6 hours
    • B. 10 hours
    • C. 15 hours
    • D. 30 hours
    • Discuss
    • 8. Two pipes A and B can fill a tank in 20 and 30 minutes respectively. If both the pipes are used together, then how long will it take to fill the tank?

    • Options
    • A. 12 min
    • B. 15 min
    • C. 25 min
    • D. 50 min
    • Discuss
    • 9. Three taps A, B and C can fill a tank in 12, 15 and 20 hours respectively. If A is open all the time and B and C are open for one hour each alternately, the tank will be full in:

    • Options
    • A. 6 hours
    • B.
      6 2 hours
      3
    • C. 7 hours
    • D.
      7 1 hours
      2
    • Discuss
    • 10. Two pipes A and B can fill a cistern in 37½ minutes and 45 minutes respectively. Both pipes are opened. The cistern will be filled in just half an hour, if the B is turned off after:

    • Options
    • A. 5 min.
    • B. 9 min.
    • C. 10 min.
    • D. 15 min.
    • Discuss


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