Posted On:March 2, 2019, Posted By: Latest Interview Questions,
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Dear Readers, Welcome to __ Pipes and Cistern - Aptitude Objective Questions__ have been designed specially to get you acquainted with the nature of questions you may encounter during your Job interview for the subject of

**1.Inlet :**

A pipe connected with a tank or a cistern or a reservoir, that fills it, is known as an inlet.

**Outlet :**

A pipe connected with a tank or cistern or reservoir, emptying it, is known as an outlet.

**2. If a pipe can fill a tank in x hours, then :**

part filled in 1 hour = 1 / x.

**3. I. If a pipe can empty a tank in y hours, then :**

part emptied in 1 hour = 1 / y.

II. If a pipe can fill a tank in x hours and another pipe can empty the full tank in y hours (where y > x), then on opening both the pipes,

then the net part filled in 1 hour = (1 / x - 1 / y).

III. If a pipe can fill a tank in x hours and another pipe can empty the full tank in y hours (where y > x), then on opening both the pipes,

then the net part emptied in 1 hour = (1 / y - 1 / x).

A. 4 hrs 30 min

B. 7 hrs 30 min

C. 8 hrs 10 min

D. None of these

Answer: B

**Explanation:**

Net part filled in 1 hour = (1/10) + (1/12)-(1/20) = (8/60) = (2/15).

The tank will be full in 15/2 hrs = 7 hrs 30 min.

A. 14 hours

B. 16 hours

C. 18 hours

D. 21 hours

Answer: D

**Explanation:**

Work done by the leak in 1 hour= (1/3)-(1/ (7/2))

= (1/3)-(2/7) = (1/21).

The leak will empty .the tank in 21 hours.

A. 17 min

B. 24 min

C. 28 min

D. 39 min

Answer: D

**Explanation:**

Part filled in 7 min. = 7*((1/36) + (1/45)) = (7/20).

Remaining part= (1-(7/20)) = (13/20).

Net part filled in 1 min. when A, B and C are

opened= (1/36) + (1/45)-(1/30) = (1/60).

Now, (1/60) part is filled in one minute.

(13/20) part is filled in (60*(13/20)) =39 minutes.

A. 5 min

B. 14 min

C. 8 min

D. 19 min

Answer: C

**Explanation:**

Let B be closed after x min. then,

Part filled by (A+B) in x min. +part filled by A in (18-x) min = 1

Therefore x*((1/24) + (1/32)) + (18-x)*(1/24) =1

=> (7x/96) + ((18-x)/24) =1.

=> 7x +4*(18-x) =96.

Hence, be must be closed after 8 min.

A. 12 min

B. 15 min

C. 25 min

D. 50 min

Answer: A

**Explanation:**

Part filled by A in 1 min = 1/20

Part filled by B in 1 min = 1/30

Part filled by (A + B) in 1 min = (1/20 + 1/30) = 1/12

Both pipes can fill the tank in 12 minutes.

A. 2

B. 2.5

C. 3

D. 3.5

**Explanation:**

part filled by (A+B+C) in 1 hour = (1/5 + 1/6 + 1/30)

‹=› 1/3.

All the three pipes together will fill the tank in 3 hours.

A. 5/11

B. 6/11

C. 7/11

D. 8/11

**Solution:**

Part filled by (A + B + C) in 3 minutes = 3(1/30+1/20+1/10)

= (3×11/60)

= 11/20.

Part filled by C in 3 minutes = 3/10.

Required ratio = (3/10×20/11)

= 6/11.

A. 8 hrs

B. 9 hrs

C. 18 hrs

D. 36 hrs

**Solution:**

Part filled by (A + B) in 1 hour = (1/5 + 1/20)

= 1/4.

So, A and B together can fill the tank in 4 hours.

Work done by the leak in 1 hour = (1/4 - 2/9)

= 1 / 36.

Therefore, Leak will empty the tank in 36 hrs.

A. 8

B. 15

C. 16

D. 18

Answer: D

**Explanation: **

Capacity of the tank = (12 * 13.5) litres = 162 litres.

Capacity of each bucket = 9 litres

Number of buckets needed = (162/9) = 18.

A. 5 hrs

B. 7 hrs

C. 6 hrs

D. 8 hrs

Answer: C

**Explanation: **

Net part filled in 1 hour = (1/2) - (1/3) = 1/6

Cistern will be full in 6 hours.

A. filled in 12 min

B. filled in 8 min

C. emptied in 12 min

D. emptied in 8 min

Answer: D

**Explanation:**

Rate of waste pipe being more, the tank will be emptied when both the pipes are opened.

Net emptying work done by both in 1 min = (1/8) - (1/16) = 1/16

Now, full tank will be emptied by them in 16 min.

Half full tank will be emptied in 8 min.

A. 3 min and 30 sec.

B. 4 min and 30 sec.

C. 4 min.

D. 4 min 77 sec.

Answer: C

**Explanation: **

A tank can be filled by a tap in 20 minutes and by another tap in 6O minutesLet B be closed after x minutes. Then,

Part filled by (A + B) in x min. + Part filled by A in (9 — x) min, = 1

x[(1/12) + (1/16)] + (9 - x)(1/12) = 1 or (7x/48) + (9-x)/12 = 1

or7x + 36 — 4x = 48 or x=4.

So, B must be closed after 4 minutes.

A. 10 min

B. 15 min

C. 12 min

D. 20 min

Answer: D

Part filled in 10 min = 10[(1/20) + (1/60)] = 10 * (4/60) = 2/3

Remaining part = (1 - (2/3)) = 1/3

Part filled by second tap in 1 min = 1/60

(1/60) : (1/3) ? 1 : x

Hence, the remaining part will be filled in 20 min.

A. 5260

B. 5846

C. 5760

D. 6970

Answer: C

**Explanation: **

Work done by the inlet in 1 hour = (1/6) - (1/8) = 1/24

Work done by the inlet in 1 min = (1/24) * (1/60) = 1/1440

Volume of 1/1440 part = 4 liters.

Volume of whole = (1440 * 4) litres = 5760 litres.

A. 5 hrs

B. 12 and 1/2 hrs

C. 6 hrs

D. 7 and 1/2 hrs

Answer: C

**Explanation: **

A's hours work=1/10, B's 1 hours work = 1/15,

(A+B)s 1 hours work = (1/10) + (1/15) = 5/30 = 1/6

Both the taps can fill the tank in 6 hours.

A. 10 hours 30 min

B. 21 hours

C. 12 hours

D. 24 hours

Answer: B

**Explanation: **

Work done by the leak in 1 hour = (1/3) - (2/7) = 1/21 .

Leak will mpty the tank in 21 hours.

A. 5

B. 12

C. 10

D. 15 and 2/3

Answer: A

**Explanation: **

Part filled by (A +B+ c) in 1 min. = (1/20) +(1/15) + (1/12) = 12/60 = 1/5

All the three pipes together will fill the tank in 5 min.

A. 4.5 hrs

B. 6.5 hrs

C. 5 hrs

D. 7.2 hrs

Answer : D

**Explanation :**

Net part filled in 1 hour = (1/4 - 1/9) = 5/36

The cistern will be filled in 36/5 hrs i.e., 7.2 hrs.