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Q:

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 & Explanation Answer: 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 : 8/15 :: 1:x

x = (8/15*1*20) = $10 \frac{2}{3} m i n = 10 m i n 40 s e c$

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

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Filed Under: Pipes and Cistern

Q:

Two pipes can fill a tank in 20 and 24 minutes respectively and a waste pipe can empty 3 gallons per minute. All the three pipes working together can fill the tank in 15 minutes. The capacity of the tank is:

A) 60 gallons	B) 100 gallons
C) 120 gallons	D) 180 gallons

Answer & Explanation Answer: C) 120 gallons

Explanation:

Work done by the waste pipe in 1 minute = $\frac{1}{15} - (\frac{1}{20} + \frac{1}{24}) = \frac{1}{15} - \frac{11}{120} = - \frac{1}{40}$ [-ve sign means emptying]

Volume of $\frac{1}{40}$ part = 3 gallons

Volume of whole = (3 x 40) gallons = 120 gallons.

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Filed Under: Pipes and Cistern
Exam Prep: AIEEE , Bank Exams , CAT
Job Role: Bank Clerk , Bank PO

Q:

A pump can fill a tank with water in 2 hours. Because of a leak, it took $2 \frac{1}{3}$ hours to fill the tank. The leak can drain all the water of the tank in:

A) 7 hours	B) 8 hours
C) 12 hours	D) 14 hours

Answer & Explanation Answer: D) 14 hours

Explanation:

If the total area of pump=1 part

The pumop take 2 hrs to fill 1 part

The pumop take1 hour to fill 1/2 portion

Due to lickage

The pumop take 7/3 hrs to fill 1 part

The pumop take1 hour to fill 3/7 portion

Now the difference of area = (1/2-3/7)=1/14

This 1/14 part of water drains in 1 hour

Total area=1 part of water drains in (1x14/1)hours= 14 hours

So the leak can drain all the water of the tank in 14 hours.

Leak will empty the tank in 14 hrs

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Filed Under: Pipes and Cistern
Exam Prep: CAT , Bank Exams , AIEEE
Job Role: Bank PO , Bank Clerk

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 & Explanation 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 =4*1/6 =2/3

Remaining part = $(1 - \frac{1}{2}) = \frac{1}{2}$

$\frac{2}{3} : \frac{1}{2} : : 1 : x$

=> x = $(\frac{1}{2} * 1 * \frac{3}{2}) = \frac{3}{4}$

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

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Filed Under: Pipes and Cistern

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 & Explanation Answer: C) 14

Explanation:

Part filled in 2 hours = 2/6=1/3

Remaining part = $(1 - \frac{1}{3}) = \frac{2}{3}$

(A + B)'s 7 hour's work = 2/3

(A + B)'s 1 hour's work = 2/21

C's 1 hour's work = { (A + B + C)'s 1 hour's work } - { (A + B)'s 1 hour's work }

=1/6-2/21 = 1/14

C alone can fill the tank in 14 hours.

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Filed Under: Pipes and Cistern

Q:

Find out the wrong number in the series.

7, 8, 18, 57, 228, 1165, 6996

A) 8	B) 18
C) 57	D) 228

Answer & Explanation Answer: D) 228

Explanation:

Let the given numbers be A, B, C, D, E, F, G.

Then, A, A x 1 + 1, B x 2 + 2, C x 3 + 3, D x 4 + 4, E x 5 + 5, F x 6 + 6 are the required numbers.

Clearly, 228 is wrong.

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Filed Under: Odd Man Out

Q:

Insert the missing number.

7, 26, 63, 124, 215, 342, (....)

A) 391	B) 421
C) 481	D) 511

Answer & Explanation Answer: D) 511

Explanation:

Numbers are (2³ - 1), (3³ - 1), (4³ - 1), (5³ - 1), (6³ - 1), (7³ - 1) etc.

So, the next number is (8³ - 1) = (512 - 1) = 511.

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Filed Under: Odd Man Out

Q:

Insert the missing number.

8, 7, 11, 12, 14, 17, 17, 22, (....)

A) 20	B) 22
C) 24	D) 27

Answer & Explanation Answer: A) 20

Explanation:

There are two series (8, 11, 14, 17, 20) and (7, 12, 17, 22) increasing by 3 and 5 respectively.

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Filed Under: Odd Man Out

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