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

18 pipes of equal capacity fills the tank in 20 minutes. How many pipes of equal capacity may be required to fill the tank exactly in 15 minutes ? समान क्षमता वाले 18 नल पानी की टंकी को 20 मिनट में भर देते हैं | उसी नल को 15 मिनट में भरने के लिए समान क्षमता वाले कितने नलों की आवश्यकता होगी ?

  1. 20

  2. 24

  3. 30

  4. 36
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

18 pipes fill tank in 20 minutes. This is an inverse proportion: more pipes = less time. 18 × 20 = X × 15, where X is required pipes. X = (18 × 20)/15 = 360/15 = 24 pipes. The work (filling the tank) is constant. Pipes × Time = Constant. When time decreases from 20 to 15 minutes (factor of 3/4), pipes must increase by factor 4/3: 18 × 4/3 = 24.

Multiple choice

Two pipes A and B can fill a tank in 12 minutes working together. If pipe A can fill the tank in 20 minutes, the time taken to fill the tank by B is - दो पाइप A और B एक टंकी को 12 मिनट में भर सकते हैं। यदि पाइप A टंकी को 20 मिनट में भर सकती है, तो पाइप B द्वारा टंकी को भरने में लिया गया समय है -

  1. 25 minutes/मिनट

  2. 18 minutes/मिनट

  3. 30 minutes/मिनट

  4. 40 minutes/मिनट
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

When pipes work together, their rates add up. Pipe A's rate is 1/20 tank per minute. The combined rate of A and B is 1/12 tank per minute. Therefore, B's rate is 1/12 - 1/20 = 1/30 tank per minute, which means B alone takes 30 minutes to fill the tank.

Multiple choice

One pipe can fill a water tank in 40 minutes and another pipe can make the filled tank empty in 60 minutes. If both the pipes are open, in how many hours will the empty tank be filled?

  1. 2 hours

  2. 2.5 hours

  3. 3 hours

  4. 3.5 hours
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

First pipe fills in 40 minutes (rate = +1/40 tank per minute). Second pipe empties in 60 minutes (rate = -1/60 tank per minute). Combined rate = 1/40 - 1/60 = (3-2)/120 = 1/120 tank per minute. Time to fill = 120 minutes = 2 hours.

Multiple choice

Water flows into a tank which is 200 m long and 150 m wide, through a pipe of cross-section (0.3m \times 0.2m) at 20 km/h. In what time will the water level be 8m?

  1. 200 hr

  2. 250 hr

  3. 350 hr

  4. 450 hr

  5. 500 hr
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The tank volume needed is 200 × 150 × 8 = 240,000 m³. The pipe cross-section is 0.3 × 0.2 = 0.06 m² and water flows at 20 km/h = 20,000 m/h, giving a flow rate of 0.06 × 20,000 = 1,200 m³/h. Time = volume/flow rate = 240,000/1,200 = 200 hours.

Multiple choice

A tank can be filled by three pipes A, B, C in 12 hrs, 20 hrs and 16 hrs respectively. Each pipe is open for one hour alternatively starting with A and followed by B and C respectively, if a drainage pipe is open alone for every seventh hour then tank will be filled in 22 hour and 40 minute. Find in how many hours the drainage pipe can empty the tank alone?

  1. 6

  2. 8

  3. 11

  4. 13

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

In 21 hours (3 cycles of 7 hours each): A, B, C work for 3 hours each, drainage works for 3 hours. Net work = 3*(1/12 + 1/20 + 1/16) - 3/D = 43/60 - 3/D. Remaining work in hour 22 (A) + 23 (B): 1/12 + 1/20 = 8/60. Total work = 43/60 + 8/60 = 51/60. Remaining 9/60 done by C in 24th hour, but drainage opens in 22nd hour. The correct drainage rate is 40/3 hrs (approximately 13.33), which is not in options A-D.

Multiple choice

Two pipes A and B can fill a tank at the rate of 3 lit./min. and 4 lit. /min. respectively. If A can alone fill the tank in 14 min, then in how much time both pipe can fill it. A और B दो नल किसी टंकी को क्रमशः 3 लीटर प्रति मिनट तथा 4 लीटर प्रति मिनट की दर से भरते हैं। यदि A अकेले किसी टंकी को 14 मिनट में भरता है तो दोनों मिलकर उसे कितनी देर में भरेगें?

  1. 6 min./मि.

  2. 7 min./मि.

  3. 2 min./मि.

  4. 5 min./मि.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Pipe A fills at 3 lit/min, taking 14 min, so tank capacity = 3×14 = 42 lit. Pipe B fills at 4 lit/min. Combined rate = 3+4 = 7 lit/min. Time = 42/7 = 6 min. Options B, C, D are incorrect.

Multiple choice

Pipe A is 3 times more efficient than B & takes 15 min less time to fill bucket. How many litre water will be filled by both pipes if they fill 7 l/min water together. पाइप A,B से तीन गुना अधिक सक्षम है और एक बाल्टी को भरने में 15 मिनट कम समय लगता है। यदि वे मिलकर 1 मिनट में 7 लीटर पानी भरते हो तो दोनों पाइपों के द्वारा कितने लीटर पानी भरा जाएगा ?

  1. 20 l/ली.

  2. 24 l/ली.

  3. 26 l/ली.

  4. 28 l/ली.
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Let B's rate be x L/min, so A's rate is 4x L/min. Together: 5x = 7, so x = 1.4 and A's rate = 5.6 L/min. Time ratio: 5.6t₁ = 1.4t₂ (same work), with t₂ - t₁ = 15. Solving gives bucket = 28 litres. This is a work and time problem with efficiency ratios.

Multiple choice

If two pipes operates simultaneously, a tank is filled in 12 hours. One pipe fills the tank in 10 hours faster than the other. In how many hours does the faster pipe alone take to fill the tank? यदि दो नलियाँ एक साथ चालू हों, तो एक टंकी 12 घंटों में भर जाती है। उनमें एक नली उस टंकी को दूसरी की अपेक्षा 10 घंटे अधिक की गति से भर देती है। तदनुसार, वह तेज गति वाली नली अकेली, उस टंकी को कितने घंटों में भर देगी?

  1. 20

  2. 18

  3. 15

  4. 12
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Let slower pipe take x hours, so faster takes (x-10) hours. Together: 1/x + 1/(x-10) = 1/12. Solving: (2x-10)/[x(x-10)] = 1/12, giving x² - 10x = 24x - 120, so x² - 34x + 120 = 0. This gives x = 30 (valid) or x = 4 (invalid as x-10 would be negative). Faster pipe takes 30-10 = 20 hours.

Multiple choice

Two pipes A and B can separately fill a tank in 5 hrs. and 20 hrs. respectively .Both the pipes are opened together ,but due to a hole in bottom ,it takes 30 min. more to fill the tank.If the tank is full and the pipes A and B turned off.In what time will the hole at the bottom empty the tank ? दो पाइप A और B एक टंकी को अलग- अलग क्रमशः 5 घं. और 20 घं. में भर सकते है। दोनों पाइप एक साथ खोल दिये जाते है लेकिन तली में एक छेद होने के कारण टंकी को भरने में 30 मिनट अधिक लगते है। यदि टंकी पूरी भरी हो और दोनों पाइप बन्द हो तो तली का छेद टंकी को कितने समय में खाली कर देगा?

  1. 24 hrs.

  2. 36 hrs.

  3. 48 hrs.

  4. 62 hrs.
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Combined rate of A + B = 1/5 + 1/20 = 1/4 tank per hour (4 hours to fill). With hole, it takes 4.5 hours, so effective rate = 2/9 per hour. Hole's rate = 1/4 - 2/9 = 1/36 per hour (emptying). The hole alone empties the full tank in 36 hours.

Multiple choice

One pipe can fill a tank three time as fast as another pipe. If together the two pipes can fill the tank in 48 minutes. The slower pipe alone will be able to fill the tank in - एक पाइप दूसरे पाइप की अपेक्षा एक टंकी को तीन गुना तेजी से भर सकता है। यदि वे दोनों पाइप एक साथ टंकी को 48 मिनट में भर देता है। तो धीमी गति वाला पाइप टंकी को अकेले भरने में सक्षम होगा-

  1. 205 m./मिनट

  2. 192 m./मिनट

  3. 184 m./मिनट

  4. 164 m./मिनट
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Let slower pipe time = x minutes. Then faster pipe time = x/3 minutes (3 times faster). Their combined rate: 1/x + 3/x = 4/x = 1/48 (since together they fill in 48 min). Solving: 4/x = 1/48, so x = 192 minutes for slower pipe alone.

Multiple choice

A tank can be filled with water by two pipes A and B together in 36 hours. If the pipe B was stopped after 30 hours, the tank is filled in 40 hours. The pipe B can alone fill the tank in

  1. 45 hours

  2. 60 hours

  3. 75 hours

  4. 90 hours
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Combined rate of A and B: 1/36 tank per hour. In first scenario: A+B work for 30 hours, then A works alone for 10 hours (total 40 hours). So 30(1/36) + 10(1/A) = 1 tank, where 1/A is A's rate. This gives 5/6 + 10/A = 1, so 10/A = 1/6 and A alone takes 60 hours. Since 1/A + 1/B = 1/36, we have 1/60 + 1/B = 1/36, giving 1/B = 1/36 - 1/60 = 1/90. So B alone takes 90 hours. Option D is correct.

Multiple choice

Pipe L is 6 times faster than second pipe K. If pipe K can fill a cistern in 21 minutes, then find the time when the cistern will be full if both the pipes are opened together ? पाइप L दूसरी पाइप ज्ञ से 6 गुना तेज है। यदि पाइप K टंकी को 21 मिनट में भर सकता है तो दोनों पाइप मिलकर टंकी को कितने समय में भर लेंगे?

  1. 7 minutes/ मिनट

  2. 5 minutes/ मिनट

  3. 8 minutes/ मिनट

  4. 3 minutes/ मिनट
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

K fills in 21 min, so rate = 1/21. L is 6 times faster: rate = 6/21. Combined rate = 7/21 = 1/3. Time = 3 minutes. Option D is correct.

Multiple choice

A pipe can fill a tank in 12 hours. After half the tank is filled, three more similar pipes are opened. What is the total time to fill the tank completely? एक पाइप किसी टंकी को 6 घंटे में भर सकता है | आधी टंकी भरने के बाद, इसी प्रकार के तीन और नल खोल दिए जाते हैं | टंकी को पूरा भरने के लिए लगा कुल समय है ?

  1. 4 hours 45 minutes/4 घंटे 45 मिनट

  2. 4 hours /4 घंटे

  3. 3 hours 45 minutes/3 घंटे 45 मिनट

  4. 45 minutes/45 मिनट
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The Hindi text (6 hours) contradicts the English text (12 hours). Using 6 hours: half tank fills in 3 hours by one pipe. Remaining half is filled by 4 pipes in 0.75 hours (3/4). Total time = 3 + 0.75 = 3 hours 45 minutes. When n similar pipes work together, time reduces by factor 1/n.

Multiple choice

Work efficiency of pipe - I is two and a half - times the work efficiency of pipe - II. If pipe - I can fill three - fifth part of the tank in 18 hours then in how many hours pipe - II will fill the whole tank alone? पाइप - I की कार्यक्षमता पाइप - II की कार्यक्षमता की ढाई गुना है | यदि पाइप - I टंकी के तीन - पांचवे भाग को 18 घंटे में भर देता है तो कितने घंटों में पाइप - II अकेले इस पूरी टंकी को भर देगा ?

  1. 45 hours/घंटे

  2. 50 hours/घंटे

  3. 60 hours/घंटे

  4. 75 hours/घंटे
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Pipe I fills 3/5 of tank in 18 hours, so it fills the whole tank in 18 × 5/3 = 30 hours. Pipe I's efficiency is 2.5 times Pipe II's efficiency, so Pipe II takes 2.5 × 30 = 75 hours to fill the tank alone. Therefore, the answer is 75 hours.