21)

Two pipes P and Q, when opened alone can fill the tank in 20 and 30 hours respectively. If both pipes are opened together, then in how many hours will the tank be filled?

A)

10 hr

B)

12 hr

C)

15 hr

D)

20 hr

22)

A cistern is normally filled in 8 hours but takes two hours 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)

20 hrs

C)

25 hrs

D)

40 hrs

23)

Two pipes A and B can fill a tank in 60 minutes and 75 minutes respectively. There is also an outlet C. If A, B and C are opened together, the tank is full in 50 minutes. How much time will be taken by C to empty the full tank?

A)

25 minutes

B)

50 minutes

C)

100 minutes

D)

200 minutes

24)

Pipe A can fill a tank in 16 minutes and pipe B can empty it in 24 minutes. If both the pipes are opened together after how many minutes should pipe B be closed, so that the tank is filled in 30 minutes?

A)

19 mins.

B)

20 mins.

C)

21 mins.

D)

22 mins.

25)

Two pipes P and Q can fill a tank in 20hrs and 25hrs respectively while a third pipe R can empty the tank in 30hrs. If all the pipes are opened together for 10hrs and then pipe R is closed then in what time the tank can be filled.

A)

100/27

B)

200/27

C)

250/27

D)

400/27

26)

Three pipes A, B and C can fill a tank from empty to full in 30 minutes, 20 minutes and 10 minutes respectively. When the tank is empty, all the three pipes are opened. A, B and C discharge chemical solutions P, Q and R respectively. What is the proportion of solution R in the liquid in the tank after 3 minutes?

A)

5/11

B)

6/11

C)

7/11

D)

8/11

27)

Pipes A and B can fill a tank in 16 hours and 24 hours, respectively, and pipe C alone can empty the full tank in x hours. All the pipes were opened together at 10:30 AM, but C was closed at 2:30 PM. If the tank was full at 8:30 PM on the same day, then what is the value of x?

A)

24 hrs

B)

48 hrs

C)

96 hrs

D)

144 hrs

28)

Pipe A and Pipe B can alone fill a tank in 20 hours and 30 hours, respectively and Pipe C alone can empty the tank in 15 hours. If pipe A opened alone for the first hour and Pipe B opened alone for the second hour and after the second hour all three pipes are opened, then the total time required to fill the tank is –

A)

55 hrs

B)

56 hrs

C)

57 hrs

D)

58 hrs

29)

Two pipes A and B can fill a tank in 6 hours and 4 hours respectively. If they are opened on alternate hours and if pipe A is opened first, then the tank shall be filled in:

A)

5 hrs

B)

10 hrs

C)

15 hrs

D)

20 hrs

30)

Two pipes A and B are attached to an empty water tank. Pipe A fills the tank while pipe B drains it. If pipe A is opened at 2 pm and pipe B is opened at 3 pm, then the tank becomes full at 10 pm. Instead, if pipe A is opened at 2 pm and pipe B is opened at 4 pm, then the tank becomes full at 6 pm. If pipe B is not opened at all, then the time, in minutes, taken to fill the tank is

A)

88 mins

B)

132 mins

C)

144 mins

D)

175 mins