16
Q:

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) 10 B) 12
C) 14 D) 16

Answer:   C) 14



Explanation:

Part filled in 2 hours ={\color{Black} \frac{2}{6}=\frac{1}{3}}

Remaining part ={\color{Black} \left ( 1-\frac{1}{3} \right )=\frac{2}{3}}

{\color{Black} \therefore } (A + B)'s 7 hour's work ={\color{Black} \frac{2}{3}}

(A + B)'s 1 hour's work ={\color{Black} \frac{2}{21}}

{\color{Black} }{\color{Black}\therefore }C's 1 hour's work = { (A + B + C)'s 1 hour's work } - { (A + B)'s 1 hour's work }

={\color{Black} \left ( \frac{1}{6}-\frac{2}{21} \right )=\frac{1}{14}}

{\color{Black} \therefore }C alone can fill the tank in 14 hours.

Q:

A and B can fill the tank in 60 min and 90 min. There is a leak at 3/4th of the height. If leak is opened alone, it takes 36 min to empty till 3/4th the height. Find the time taken to fill the tank if all of the taps and the leak are opened simultaneously.

A) 39 B) 27
C) 37 D) 33
 
Answer & Explanation Answer: A) 39

Explanation:
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10 125
Q:

Water flows into a tank which is 200 m long and 150 m wide, through a pipe of cross-section (0.3m x 0.2m) at 20 km/h. In what time will the water level be 12m  ?

A) 200 hrs B) 240 hrs
C) 300 hrs D) 270 hrs
 
Answer & Explanation Answer: C) 300 hrs

Explanation:

Volume of water collected in the tank in 1 hour

⇒ (0.3 × 0.2 × 20km × 1000mts) = 1200 m cubic

If after t hours, the water is at height of 12m,

1200t=200×150×12 

⇒ t = 300 Hours.

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6 333
Q:

A Tank is normally filled in 9 hours but takes four hours longer to fill because of a leak in its bottom. If the tank is full, the leak will empty it in ?

A) 32.5 hrs B) 29.25 hrs
C) 30.30 hrs D) 31 hrs
 
Answer & Explanation Answer: B) 29.25 hrs

Explanation:

Let the leak will empty the tank in x hrs

Then,

1/9 - 1/x = 1/13

x = 29.25 hrs

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4 510
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) 4 hrs 15 min B) 3 hrs 24 min
C) 4 hrs 51 min D) 3 hrs 45 min
 
Answer & Explanation Answer: D) 3 hrs 45 min

Explanation:

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

Part filled by the taps in 1 hour = 4 x 1/6 = 2/3

Remaining part = 1 - 1/2 = 1/2

2/3 : 1/2 :: 1 : p

p = 1/2 x 1 x 3/2 = 3/4 hrs. i.e., 45 min

So, total time taken = 3 hrs 45 min.

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5 882
Q:

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

A) 31 min B) 29 min
C) 28 min D) 30 min
 
Answer & Explanation Answer: D) 30 min

Explanation:

Part filled by (A + B) in 1 minute = (1/60 + 1/40) = 1/24
Suppose the tank is filled in x minutes.
Then, x/2(1/24 + 1/40) = 1
(x/2) x (1/15) = 1 => x = 30 min.

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4 909