9
Q:

# A tap can fill a tank in 6 hours. After half the tank is filled, three more similar taps are opened. What is the total time taken to fill the tank completely?

 A) 3 hrs 15 min B) 3 hrs 45 min C) 4 hrs 15 min D) 4 hrs 1

Answer:   B) 3 hrs 45 min

Explanation:

Time taken by one tap to fill half of the tank = 3 hrs.

Part filled by the four taps in 1 hour =${\color{Black}&space;\left&space;(&space;4\times&space;\frac{1}{6}&space;\right&space;)=\frac{2}{3}}$

Remaining part =${\color{Black}&space;\left&space;(&space;1-&space;\frac{1}{2}&space;\right&space;)=\frac{1}{2}}$

${\color{Black}&space;\therefore&space;\frac{2}{3}:\frac{1}{2}&space;::1:x}$

${\color{Black}&space;\Rightarrow&space;x=\left&space;(&space;\frac{1}{2}&space;\times&space;1\times&space;\frac{3}{2}\right&space;)=\frac{3}{4}}$

So, total time taken = 3 hrs. 45 mins.

Q:

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

Explanation:

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.

1 19
Q:

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

 A) 15 min 20 sec. B) 16 min 40 sec. C) 13 min 10 sec. D) 14 min 40 sec.

Explanation:

Part filled in 4 minutes = 4(1/15 + 1/20) = 7/15

Remaining part = 1 - 7/15 = 8/15

Part filled by B in 1 minute = 1/20

1/20 : 8/15 :: 1 : k

k = 8/15 x 1 x 20 = 10 2/3 min = 10 min 40 sec.

The tank will be full in (4 min. + 10 min. 40 sec) = 14 min 40 sec.

3 66
Q:

Two pipes A and B can separately fill a cistern in 10 and 15 minutes respectively. A person opens both the pipes together when the cistern should have been was full he finds the waste pipe open. He then closes the waste pipe and in another 3 minutes the cistern was full. In what time can the waste pipe empty the cistern when fill  ?

 A) 8.21 min B) 8 min C) 8.57 min D) 8.49 min

Explanation:

1/10 + 1/15 = 1/6 x 3 = 1/2

1 - 1/2 = 1/2

1/10 + 1/15 - 1/x = 1/2

x = 8.57 min

1 39
Q:

Pipe A can fill a tank in 16 minutes and pipe B cam 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) 21 min B) 24 min C) 20 min D) 22 min

Explanation:

Let the pipe B be closed after 'K' minutes.

30/16 - K/24 = 1 => K/24 = 30/16 - 1 = 14/16

=> K = 14/16 x 24 = 21 min.

1 28
Q:

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) 20 hrs B) 28 hrs C) 36 hrs D) 40 hrs