Quantitative Aptitude

Pipes and Cisterns

535 Questions
All Delayed opening or closing 106 Combined pipes and the LCM shortcut 77 Find unknown pipe time 64 Efficiency ratios and faster-pipe relations 61 Flow rates based on pipe diameter 50 Leaks and reverse-rate questions 50 Actual capacity and pump-rate equations 44 Partial filling or emptying condition 44 Alternating pipes and changing phases 39

Pipes and Cisterns Questions

Multiple choice

A cistern usually can be filled by a tap in 15 hrs but due to a leak in the bottom it takes 3 hrs more to fill. If the tank is half filled find, in how many hours leak will empty it.

  1. 24

  2. 25

  3. 30

  4. 45

  5. None of these
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Tap fills in 15 hr, so fill rate = C/15 per hr. With leak, fills in 18 hr, so net rate = C/18. Leak rate = C/15 - C/18 = C/90 per hr. Time for leak to empty full tank = 90 hr. For half-filled tank (C/2), time = (C/2)/(C/90) = 45 hr.

Multiple choice

An inlet pipe A can completely fill a water tank of 25000 litres capacity in 10 hours but an outlet pipe B can empty the completely filled tank in 40 hours. Q I: In how many hours pipe A and Pipe B together will fill half of the tank? Q II: In how many hours pipe A alone fill 70% of the capacity of the tank?

  1. Q I > Q II

  2. Q I ≥ Q II

  3. Q I < Q II

  4. Q I ≤ Q II

  5. Q I = Q II or cannot be determined
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Pipe A fills at 2500 L/hr (25000÷10), Pipe B empties at 625 L/hr (25000÷40). Combined rate: 1875 L/hr. Q I: Half tank = 12500 L, time = 12500÷1875 = 6.67 hours. Q II: 70% of 25000 = 17500 L, time = 17500÷2500 = 7 hours. Since 6.67 < 7, Q I takes less time than Q II, making Q I < Q II correct.

Multiple choice

In each of the following questions, read the given statement and compare the Quantity I and Quantity II on its basis. (Only quantity is to be considered) Quantity 1- A pipe can empty a tank in 40 min. A second pipe with diameter twice much as that of the first is also attached with the tank to empty it. The two pipes together can empty the tank in how much minutes? Quantity 2- An amount will become 8 times of itself in 3 years with compound interest. Then in how much time it will become 16 times of itself?

  1. Quantity 1 > Quantity 2

  2. Quantity 1 < Quantity 2

  3. Quantity 1 ≥ Quantity 2

  4. Quantity 1 ≤ Quantity 2

  5. Quantity 1 = Quantity 2 or Relation can’t be established
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Quantity 1: First pipe empties in 40 min. Second pipe has twice diameter = 4x flow rate (flow proportional to diameter squared). Combined rate: 1/40 + 4/40 = 5/40, so time = 40/5 = 8 minutes. Quantity 2: Amount becomes 8x in 3 years means (1+r)^3 = 8, so 1+r = 2. For 16x: (1+r)^t = 16, so 2^t = 16, thus t = 4 years. 8 > 4, so Quantity 1 > Quantity 2.

Multiple choice

A tank gets filled by a pipe in 2 hours. But due to a leak, it takes 30 more minutes to fill the tank. How long will it take a full tank to get emptied by the leak, when the pipe is closed?

  1. 10 hours

  2. 2 hours 45 minutes

  3. 5 hours

  4. 2 hours 30 minutes
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Pipe rate = 1/2 tank/hour. With leak: effective rate = 1/2.5 = 2/5 tank/hour. Leak rate = 1/2 - 2/5 = 1/10 tank/hour (leak empties). So full tank empties in 10 hours by leak alone. Answer A is correct.

Multiple choice

A cistern usually can be filled by a tap in 15 hrs but due to a leak in the bottom it takes 3 hrs more to fill. If the tank is half filled find, in how many hours leak will empty it. एक टंकी एक नल द्वारा सामान्यता 15 घंटे में भर जाती है परन्तु तली में रिसाव के कारण इसे भरने में 3 घंटे अधिक लगते हैं. यदि टंकी आधी भरी हो तो रिसाव के कारण कितने घंटे में खाली हो जायेगी?

  1. 24

  2. 25

  3. 30

  4. 45

  5. None of these इनमे से कोई नहीं
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The tap fills at 1/15 per hour. With the leak, effective rate is 1/18 per hour (3 hours longer). Leak rate = 1/15 - 1/18 = 1/90 per hour. So leak alone empties full tank in 90 hours. Half tank will empty in 90/2 = 45 hours. Option D is correct.

Multiple choice

Pipe A can fill the tank in 30 hours and pipe B can fill the tank in 15 hours whereas pipe C can empty the tank 10 hours. Pipe A, B and C are opened alternately for 1 hour each. Find after how many hours the tank will be filled completely ? पाइप A टैंक को 30 घंटे में भर सकता है और पाइप B टैंक को 15 घंटे में भर सकता है जबकि पाइप C टैंक को 10 घंटे में खाली कर सकता है। पाइप A, B और C को बारी-बारी से 1 घंटे के लिए खोला जाता है। ज्ञात कीजिए कि टंकी कितने घंटे बाद पूरी तरह से भर जाएगी?

  1. 30 hours to fill 30 घंटे में भर जाएगी

  2. 25 hours to fill 25 घंटे में भर जाएगी

  3. 30 hours to empty 30 घंटे में खाली हो जाएगी

  4. 25 hours to empty 25 घंटे में खाली हो जाएगी

  5. Tank will never fill टंकी कभी नहीं भरेगी
Reveal answer Fill a bubble to check yourself
E Correct answer
Explanation

Let's analyze the net fill rate per 3-hour cycle: A fills 1/30 of tank per hour, B fills 1/15 per hour, C empties 1/10 per hour. In one 3-hour cycle (A then B then C): Fill from A = 1/30, fill from B = 1/15, empty from C = 1/10. Net per cycle = 1/30 + 1/15 - 1/10 = 1/30 + 2/30 - 3/30 = 0. The tank never fills because the net effect over each complete cycle is zero - the emptying rate of C exactly balances the combined filling rate of A and B. Option E is correct.

Multiple choice

There are total 12 pipes to fill a reservoir in which some are fill pipes where as some are empty pipes. A fill pipe takes 30 minutes to fill reservoir completely, which is 60 minutes more than time taken by an empty pipe to empty the reservoir. All working together takes 4.5 hr to completely fill the reservoir. If now one empty pipe starts working as fill pipe, what will be the time taken to fill the reservoir completely? एक जलाशय को भरने के लिए कुल 12 पाइप हैं जिसमें कुछ पाइप भरते हैं और कुछ खाली करती हैं। एक भरनें वाले पाइप को जलाशय को पूरी तरह से भरने में 30 मिनट लगते हैं, जो जलाशय को खाली करने के लिए एक खाली पाइप द्वारा निर्धारित समय से 60 मिनट अधिक है। पूरी तरह से जलाशय को भरने के लिए एक साथ काम करने में 4.5 घंटे लगते हैं। यदि अब एक खाली पाइप, भरनें वाले पाइप के रूप में काम करना शुरू कर दे, तो जलाशय को पूरी तरह से भरने में कितना समय लगेगा?

  1. 4.8 hr./घंटे

  2. 3 hr./घंटे

  3. 3.5 hr./घंटे

  4. 3.25 hr./घंटे

  5. None of these /इनमें से कोई नहीं
Reveal answer Fill a bubble to check yourself
E Correct answer
Explanation

Let f fill pipes and (12-f) empty pipes. Fill pipe rate = 1/30 per min, empty pipe rate = 1/30 per min (since it takes 60 min less, i.e., 30-60 = -30, meaning 30 min to empty). Net rate = f/30 - (12-f)/30 = (2f-12)/30 per min. In 4.5 hr (270 min): (2f-12)/30 × 270 = 1, giving f ≈ 5.56. With one empty pipe becoming fill: 6.56 fill, 5.44 empty. New rate ≈ 1.112/30 per min. Time ≈ 30/1.112 ≈ 26.97 min ≈ 0.45 hr. None of A (4.8), B (3), C (3.5), D (3.25) match.

Multiple choice

Three pipes A, B and C can fill a cistern in 36 minutes after working together for 12 minutes C is closed and A and B fill the cistern in 48 minutes. Find the time in which the cistern can be filled by pipe C. तीन पाइप एक टंकी को 36 मिनट में भर सकते है 12 मिनट काम करने के बाद C को बंद कर दिया जाता है। A और B दोनों मिलकर टंकी को 48 मिनट में भर देते है। कितने समय में पाइप C टंकी को पूरा भर सकेगा।

  1. 48

  2. 54

  3. 60

  4. 72

  5. 90
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Let A, B, C be their rates. A + B + C = 1/36. In 12 min: 12/36 = 1/3 filled, 2/3 remains. A + B fill 2/3 in 48 min, so A + B = (2/3)/48 = 1/72. Then C = 1/36 - 1/72 = 1/72. So C alone takes 72 minutes. Option D is correct.

Multiple choice

If Pipes A and B can fill a tank in 15 min and 20 mins respectively and pipe C empties the tank in 12 mins. what will be the time taken by A, B and C together to fill the tank completely? यदि पाइप A और B क्रमशः 15 मिनट और 20 मिनट में एक टैंक भर सकते हैं और पाइप C 12 मिनट में टैंक को खाली कर देता है। टैंक को पूरी तरह से भरने के लिए A, B और C द्वारा एक साथ लिया गया समय क्या होगा?

  1. 25 min 25 मिनट

  2. 30 min 30 मिनट

  3. 40 min 40 मिनट

  4. 20 min 20 मिनट

  5. 35 min 35 मिनट
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

A fills in 15 min, rate = 1/15 per min. B fills in 20 min, rate = 1/20 per min. C empties in 12 min, rate = -1/12 per min. Combined rate = 1/15 + 1/20 - 1/12 = 4/60 + 3/60 - 5/60 = 2/60 = 1/30 per min. Time to fill = 1 ÷ (1/30) = 30 minutes.

Multiple choice

The inlet to the tank can fill it in 4 hours while the outlet can empty it in 5 hrs. Both the pipes were opened at 9 AM, but after sometimes the outlet closed and it is observed that the tank was full at 5 PM. At what time was the outlet closed? एक टंकी को पाइप 4 घंटे में भर सकता है तो दूसरा पाइप उसी टंकी को 5 घंटे में खाली कर सकता है दोनों पाइप यदि सुबह 9 बजे एक साथ खोले जाये और कुछ समय बाद खाली करने वाला पाइप बंद कर दिया जाये तो टंकी 5 बजे भर जाती है तो बताइये खाली करने वाला पाइप कितने बजे बंद किया गया ?

  1. 2:20 PM

  2. 1:45 PM

  3. 2:40 PM

  4. 2:00 PM

  5. 2:15 PM
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Inlet fills at 1/4 tank/hour, outlet empties at 1/5 tank/hour. Combined net rate = 1/4 - 1/5 = 1/20 tank/hour. From 9 AM to 5 PM = 8 hours. Let outlet be open for t hours, then only inlet works for (8-t) hours. Work done: t(1/20) + (8-t)(1/4) = 1. Solving gives t = 5, so outlet closed at 9 AM + 5 hrs = 2 PM.