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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

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