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Three pipes P, Q and R can separately fill a cistern in 4, 8 and 12 hours respectively. Another pipe S can empty the completely filled cistern in 10 hours. Which of the following arrangements will fill the empty cistern in less time than others?

A.

P, Q and S are open

B.

P, R and S are open

C.

Q alone is open

D.

P and S are open

Answer with explanation

Answer: Option AExplanation

The correct answer is P, Q, and S are open

Workspace

A pipe can fill a tank in 3 hours. There are two outlet pipes from the tank which can empty it in 7 and 10 hours respectively. If all the three pipes are opened simultaneously, then the tank will be filled in –

A.

10 hours

B.

11 hours

C.

9 hours

D.

8 hours

Answer with explanation

Answer: Option BExplanation

Workspace

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

A.

14

B.

16

C.

12

D.

10

Answer with explanation

Answer: Option AExplanation

Workspace

Two pipes A and B can fill a cistern in 371/2 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:

A.

5 min.

B.

15 min.

C.

10 min.

D.

9 min.

Answer with explanation

Answer: Option DExplanation

Workspace

A.

28 Hours

B.

29 Hours 10 Min

C.

28 Hours 10 Min

D.

29 Hours

Answer with explanation

Answer: Option CExplanation

3 Hours work = (1/48+1/24-1/36) = 5/144

28* 3hours = 140/144

remaining part = 4/144 = 1/36

Now it’s A turn = 1/36-1/48

= 1/144 left

Now it’s B turn = 1/144*24 = 1/6 hour = 10 min

Total B = 28 Hours + 10 Min

Workspace

Two pipes A and B can fill a tank in 16 hrs and 12 hrs respectively. The capacity of the tank is 240 liters. Both the pipes are opened simultaneously and closed after 2 hrs. How much more water need to fill the tank?

A.

70 lit

B.

170 lit

C.

90 lit

D.

190 lit

Answer with explanation

Answer: Option BExplanation

Given A alone can fill the tank of capacity 240 lit in 16 hrs.

=> A can fill in 1 hr = 240/16 = 15 lit

=> B alone can fill the tank of capacity 240 lit in 12 hrs.

=> B can fill in 1 hr = 240/12 = 20 lit

Now, (A + B) in 1 hr = 15 + 20 = 35 lit

But they are opened for 2 hrs

=> 2 x 35 = 70 lit rae filled

Remaining water to be filled in tank of 240 lit = 240 – 70 = 170 lit.

Workspace

A.

1:1

B.

2:3

C.

5:4

D.

3:2

Answer with explanation

Answer: Option DExplanation

Initial Milk = 2/5*250*3/5 = 60 L

Water = 2/5*250*2/5 = 40 L

Rest of Tank =150 L

Pipes are opened then can fill rest of tank in 108/25 hours

H/W = constant

then (108/25)/12/x = (108/25)/18(150-x)

X = 90 = Milk, Water = 60

Final ratio = 3:2

Workspace

A.

2 fill pipes

B.

4 fill pipes

C.

6 fill pipes

D.

5 fill pipes

Answer with explanation

Answer: Option BExplanation

Let the number of fill pipes be ‘n’

Therefore, there will be (8 – n) waste pipes.

Each of the fill pipes can fill the tank in 8 hours.

Therefore, each of the fill pipes will fill 1/8th of the tank in an hour.

Hence, n fill pipes will fill n/8th of the tank in an hour.

Similarly, each of the waste pipes will drain the full tank in 6 hours.

∴ each of the waste pipes will drain 1/6th of the tank in an hour.

(8 – n) waste pipes will drain (8-n)/6th of the tank in an hour.

Between the fill pipes and the waste pipes, they drain the tank in 6 hours.

That is, when all 8 of them are opened, 1/6th of the tank gets drained in an hour.

(Amount of water filled by fill pipes in 1 hour – Amount of water drained by waste pipes 1 hour) = (1/6^{th} ) of the tank

Therefore,

(n/8) – ((8−n)/)6 = -1/6

N**ote**: The right hand side has a negative sign because the tank gets drained.

Cross multiplying and solving the equations, 14n – 64 = -8

or 14n = 56 or n = 4

Workspace

A cistern has a leak which would empty the cistern in 20 minutes. A tap is turned on which admits 4 liters a minute into the cistern, and it is emptied in 24 minutes. How many liters does the cistern hold?

A.

360 lit

B.

480 lit

C.

320 lit

D.

420 lit

Answer with explanation

Answer: Option BExplanation

1/k – 1/20 = -1/24

k = 120

120 x 4 = 480

Therefore, the capacity of the cistern is 480 liters

Workspace

Two taps can separately fill a cistern 10 minutes and 15 minutes respectively and when the waste pipe is open, they can together fill it in 18 minutes. The waste pipe can empty the full cistern in?

A.

7 min

B.

13 min

C.

23 min

D.

9 min

Answer with explanation

Answer: Option DExplanation

1/10 + 1/15 – 1/x = 1/18

x = 9

Workspace

Having the same capacity 9 taps fill up a water tank in 20 minutes. How many taps of the same capacity are required to fill up the same water tank in 15 minutes ?

A.

10 taps

B.

12 taps

C.

15 taps

D.

18 taps

Answer with explanation

Answer: Option BExplanation

Workspace

Three pipes A, B and C can fill a tank in 6 hours, 9 hours and 12 hours respectively. B and C are opened for half an hour, then A is also opened. The time taken by the three pipes together to fill the remaining part of the tank is?

A.

3 hours

B.

2 hours

C.

2 1/2 hours

D.

3 1/2 hours

Answer with explanation

Answer: Option CExplanation

Part of the tank filled by pipe B and C in half an hour

Remaining part

Part of the tank filled by three pipes in an hour

∴ Time to fill remaining part

Workspace

Taps A and B can fill a bucket in 12 minutes and 15 minutes respectively. If both are opened and A is closed after 3 minutes, how much further time would it take for B to fill the bucket?

A.

8 min 15 sec

B.

7 min 15 sec

C.

6 min 15 sec

D.

5 min 15 sec

Answer with explanation

Answer: Option AExplanation

Part filled in 3 minutes =

So it will take further 8 mins 15 seconds to fill the bucket.

Workspace

A pipe can fill a tank in x hours and another pipe can empty it in y (y > x) hours. If both pipes are open, in how many hours will the tank is filled?

A.

(x – y) hours

B.

(y – x) hours

C.

xy/(x−y) hours

D.

xy/(y-x) hours

Answer with explanation

Answer: Option DExplanation

Workspace

A.

16 min

B.

12 min

C.

14 min

D.

20 min

Answer with explanation

Answer: Option BExplanation

Let the efficiencies of filling pipes is 4p and 5p respectively.

Efficiency of pipe which empty the tank = 2/3 x 9p/2 = 3p

Total work = 3p x 36 = 108p

Time to fill the tank by both the pipes = 108p/9p = 12 min.

Workspace

A.

5/11

B.

6/11

C.

7/11

D.

8/11

Answer with explanation

Answer: Option BExplanation

Workspace

A tank is filled in eight hours by three pipes K, L and M. Pipe K is twice as fast as pipe L, and L is twice as fast as M. How much time will pipe L alone take to fill the tank ?

A.

32 hrs

B.

24 hrs

C.

28 hrs

D.

26 hrs

Answer with explanation

Answer: Option CExplanation

1/K + 1/L + 1/M = 1/8 (Given)

Also given that K = 2L and L = 2M

=> 1/2L + 1/L + 2/L = 1/8

=> (1 + 2 + 4)/2L = 1/8

=> 2L/7 = 8

=> L = 28 hours.

Workspace

A.

3 21/47 min

B.

4 1/2 min

C.

3 9 15/16 min

D.

None of these

Answer with explanation

Answer: Option AExplanation

Let cistern will be full in x min. Then part filled by A in x min + part filled by

B in (x-2) min + part filled by C in (x-4) min = 1

⇒ x/12 + (x-2)/16 + (x-4)/20 = 1 ⇒ 47x – 78 = 240⇒ x = 162/47 = 3 21/47 min

Workspace

A tap can fill a tank in 15 minutes, while another tap can empty the tank in 20 minutes. When the tank is already half full, both the taps are opened together. The tank will be filled up completely in the next:

A.

40 minutes

B.

30 minutes

C.

32 minutes

D.

36 minutes

Answer with explanation

Answer: Option BExplanation

Part of tank filled in one minute when both the taps are open =

Workspace

A tank can be filled by two pipes A and B in 60 minutes and 40 minutes respectively. How many minutes will it take to fill the tank from empty state if B is used for the first half time and then A and B fill it together for the other half.

A.

15 mins

B.

20 mins

C.

25 mins

D.

30 mins

Answer with explanation

Answer: Option DExplanation

Let the total time be x mins.

Part filled in first half means in x/2 = 1/40

Workspace

A pipe can empty a tank in 12 minutes and another pipe can empty it in 16 minutes. If both the pipes are opened simultaneously, find the time in which a full tank is emptied?

A.

6 minutes

B.

6(1/7) minutes

C.

6(2/7) minutes

D.

None of these

Answer with explanation

Answer: Option DExplanation

Pipes A and B can empty the tank in 12 and 16 minutes respectively.

Therefore,part empty by pipe A in 1 hour = 1/12

part empty by pipe B in 1 hour = 1/16

the quantity empty if all the pipes are opened together = 1/12 + 1/16

==> [(16+12)/ 192] ( L. C. M of 16 & 12)

==> (28 / 192)

==> (7 / 48)

Required time = 48 / 7 = 6(6/7)minutes

Workspace

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

A.

24 hrs

B.

28 hrs

C.

32 hrs

D.

36 hrs

Answer with explanation

Answer: Option BExplanation

1/A + 1/B + 1/C = 1/8 (Given)

Also given that A = 2B and B = 2C

=> 1/2B + 1/B + 2/B = 1/8

=> (1 + 2 + 4)/2B = 1/8

=> 2B/7 = 8

=> B = 28 hrs.

Workspace

A cistern is normally filled in 8 hrs. but takes 2 hrs. longer to fill because of a leak in its bottom. If the cistern is full, the leak will empty it in?

A.

16 hrs

B.

40 hrs

C.

25 hrs

D.

20 hrs

Answer with explanation

Answer: Option BExplanation

Here x = 8 hrs. and y = 8 + 2 = 10 hrs.

Now, applying the given rule, we have the

Required answer = (8 x 10) /(10 – 8) = 40 hrs.

Workspace

A leak in the bottom of a tank can empty the full tank in 6 hours. An inlet pipe fills water at the rate of 4 litres a minute. When the tank is full, the inlet is opened and due to the leak the tank is empty in 8 hours. The capacity of the tank (in litres) is

A.

5780 litres

B.

5770 litres

C.

5760 litres

D.

5750 litres

Answer with explanation

Answer: Option CExplanation

Workspace

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:

A.

14

B.

12

C.

20

D.

18

Answer with explanation

Answer: Option AExplanation

Workspace

Two pipes can fill a tank in 8 hrs & 6 hrs respectively. If they are opened on alternate hours and if pipe A gets opened first, then in how many hours, the tank will be full?

A.

6 hrs

B.

7 hrs

C.

8 hrs

D.

14 hrs

Answer with explanation

Answer: Option BExplanation

Pipe A’s work in 1 hr = 1/8

Pipe B’s work in 1 hr = 1/6

Pipes (A+B)’s work in first 2 hrs when they are opened alternately = 1/8 + 1/6 = 7 /24

Now,

In 4 hrs they fill : 2 X (7/24) = 7/12

In 6 hrs they fill : 3 X (7/24) = 7/8

After 6 hrs, part left empty = 1/8

Now it is A’s turn to open up.

In one hr it fills 1/8 of the tank.

So, the tank will be full in = 6 hrs + 1 hr = 7 hrs

Workspace

Two pipes function simultaneously the reservoir will be filled in 12 hours. One pipe fills reservoir 10 hours faster than the other. How many hours does the faster pipe take to fill the reservoir?

A.

25 hrs

B.

28 hrs

C.

20 hrs

D.

35 hrs

Answer with explanation

Answer: Option CExplanation

1/x + 1/(x + 10) = 1/12

x = 20

Workspace

Pipe A can fill a tank in 5 hours, pipe B in 10 hours and pipe C in 30 hours. If all the pipes are open, in how many hours will the tank be filled?

A.

2

B.

3

C.

3.5

D.

4

Answer with explanation

Answer: Option BExplanation

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.

Workspace

25 outlets working 6 hours a day, can empty a reservoir in 10 days. If only 15 outlets are operational and work for 4 hours a day, in how many days the reservoir can be emptied?

A.

20 days

B.

18 days

C.

25 days

D.

22 days

Answer with explanation

Answer: Option CExplanation

Apply formula used in work and time problems; M1D1T1W2 = M2D2T2W1

M1= 25 outlets, D1=10 days, T1= 6 hours/day, W2 = to fill the reservoir

M2= 15 outlets, D2=? T2 = 4 hours/day, W1= to fill the reservoir

W1=W2

So we have; M1D1T1= M2D2T2

25*10*6=15*D2*4

1500 = 60 * D2

D2=1500/60=25 days

Workspace

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