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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.

61/7 minutes

C.

62/7 minutes

D.

None of these

Answer with explanation

Answer: Option DExplanation

Pipes A and B can fill the tank in 12 and 16 hours respectively. Therefore,

part filled by pipe A in 1 hour = 1/12

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

the quantity filled 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

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 hours

B.

28 hours

C.

32 hours

D.

36 hours

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 hours.

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

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

Two pipes A and B can fill a tank in 15 minutes and 20 minutes respectively. Both the pipes are opened together but after 4 minutes, pipe A is turned off. What is the total time required to fill the tank?

A.

10 min. 20 sec.

B.

11 min. 45 sec.

C.

12 min. 30 sec.

D.

14 min. 40 sec.

Answer with explanation

Answer: Option DExplanation

Workspace

A.

24 hrs

B.

28 hrs

C.

32 hrs

D.

36 hrs

Answer with explanation

Answer: Option BExplanation

Explanation:

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 hours.

Workspace

A cistern has three pipes, A, B and C. The pipes A and B can fill it in 4 and 5 hours respectively and C can empty it in 2 hours. If the pipes are opened in order at 1, 2 and 3 A.M. When will the cistern be empty?

A.

3 PM

B.

4 PM

C.

5 PM

D.

7 PM

Answer with explanation

Answer: Option CExplanation

1 to 2 = 1/4

2 to 3 = 1/4 + 1/5 = 9/20

After 3 AM = 1/4 + 1/5 – 1/2 = -1/20

1/4 + 9/20 = 14/20

1 h —- 1/20

? —– 14/20

14 hours ==> 5 PM

Workspace

A.

25 hrs

B.

20 hrs

C.

28 hrs

D.

35 hrs

Answer with explanation

Answer: Option BExplanation

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

x = 20

Workspace

Two pipes A and B can separately fill a tank in 12 and 15 minutes respectively. A third pipe C can drain off 45 liters of water per minute. If all the pipes are opened, the tank can be filled in 15 minutes. What is the capacity of the tank

A.

480 liters

B.

540 liters

C.

600 liters

D.

675 liters

Answer with explanation

Answer: Option BExplanation

1/12 + 1/15 – 1/x = 1/15

x = 12

12 * 45 = 540

Workspace

3 pipes when opened for 3 hours can fill 3 buckets. How many buckets can 2 pipes open for 2 hours approximately fill?

A.

2/3 bucket

B.

4/3 bucket

C.

2 buckets

D.

1 bucket

Answer with explanation

Answer: Option BExplanation

2 pipes open for 2 hours will fill = (2/3) x (2/3) x 3 = 4/3 buckets

Workspace

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