91. Having the same capacity 9 taps fill up a water tank in 20 minutes. How many taps of the same capacity are required to fill up the same water tank in 15 minutes ?
    

1. 1. 10
      

   
   
   

   2. 12
      

   
   
   

   3. 15
      

   
   
   

   4. 18

   
   
   

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1. View Hint View Answer Discuss in Forum

   Here , M₁ = 9 taps , D₁ = 20 minutes , M₂ = ? , D₂ = 15 minutes
   Using the given formula ,
   M₁ D₁ = M₂ D₂
   ⇒ 9 × 20 = M₂ × 15
   

   Correct Option: B

   Here , M₁ = 9 taps , D₁ = 20 minutes , M₂ = ? , D₂ = 15 minutes
   Using the given formula ,
   M₁ D₁ = M₂ D₂
   ⇒ 9 × 20 = M₂ × 15
   

   ⇒ M2 =	9 × 20	= 12 pipes
   	15

   
   Note : Same relation as men and days is applicable

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92. A tap can empty a tank in 30 minutes. A second tap can empty it in 45 minutes. If both the taps operate simultaneously, how much time is needed to empty the tank ?
    

1. 1. 30 minutes
      

   
   
   

   2. 18 minutes
      

   
   
   

   3. 14 minutes
      

   
   
   

   4. 15 minutes

   
   
   

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1. View Hint View Answer Discuss in Forum

   As per the given in question , we have
   

   Part of tank emptied by both pipes in 1 minute =	1	+	1	=	3 + 2
   	30		45		90

   
   

   Correct Option: B

   As per the given in question , we have
   

   Part of tank emptied by both pipes in 1 minute =	1	+	1	=	3 + 2
   	30		45		90

   
   

   Part of tank emptied by both pipes in 1 minute =	5	=	1
   	90		18

   
   ∴ Required time = 18 minutes

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93. Two pipes can independently fill a bucket in 20 minutes and 25 minutes. Both are opened together for 5 minutes after which the second pipe is turned off. What is the time taken by the first pipe alone to fill the remaining portion of the bucket?
    

1. 1. 11 minutes
      

   
   
   

   2. 16 minutes
      

   
   
   

   3. 20 minutes
      

   
   
   

   4. 15 minutes

   
   
   

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1. View Hint View Answer Discuss in Forum

   On the basis of given details in question ,
   

   Part of bucket filled by both pipes in 5 minutes = 5		1	+	1
   		20		25

   
   

   Part of bucket filled by both pipes in 5 minutes = 5		5 + 4		=	9
   		100			20

   
   

   Correct Option: A

   On the basis of given details in question ,
   

   Part of bucket filled by both pipes in 5 minutes = 5		1	+	1
   		20		25

   
   

   Part of bucket filled by both pipes in 5 minutes = 5		5 + 4		=	9
   		100			20

   
   

   Remaining part = 1 –	9	=	11
   	20		20

   This remaining part will be filled by first pipe.
   

   ∴ Required time =	11	× 20 = 11 minutes
   	20

   
   

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94. Pipe 1 and 2 can fill a tank alone in 6 hours and 9 hours respectively. Pipe 3 can empty the full tank in 18 hours. If all the 3 pipes are opened simultaneously, then how much time is required to fill the tank completely?
    

1. 1. 2 hours
      

   
   
   

   2. 3.6 hours
      

   
   
   

   3. 4.5 hours
      

   
   
   

   4. cannot be filled

   
   
   

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1. View Hint View Answer Discuss in Forum

   From the given question ,
   

   Work done in 1 hour by all 3 pipes =	1	+	1	-	1	=	4
   	6		9		18		18

   
   

   Correct Option: C

   From the given question ,
   

   Work done in 1 hour by all 3 pipes =	1	+	1	-	1	=	4
   	6		9		18		18

   
   

   ∴ Time required to fill the tank completely =	18	= 4.5 hours
   	4

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95. Pipe A and B can fill a tank in 12 and 15 hours respectively. An outlet pipe C, can empty it in 6 hours. Initially pipes A and B are opened together, and after 5 hours pipe C is also opened. Find the time required to empty the tank?
    

1. 1. 45 hours
      

   
   
   

   2. 50 hours
      

   
   
   

   3. 60 hours
      

   
   
   

   4. None of these

   
   
   

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1. View Hint View Answer Discuss in Forum

   As per the given in question , we have
   

   Tank filled by A & B in 5 hours = 5		1	+	1		=	9 × 5	=	3
   		12		15			60		4

   
   

   Work done in 1 hour when all 3 pipes are opened =	1	+	1	-	1	=	9 - 10	=	- 1
   	12		15		6		60		60

   
   Since the result (or net effect) is negative, hence tank would be emptied.
   

   Correct Option: A

   As per the given in question , we have
   

   Tank filled by A & B in 5 hours = 5		1	+	1		=	9 × 5	=	3
   		12		15			60		4

   
   

   Work done in 1 hour when all 3 pipes are opened =	1	+	1	-	1	=	9 - 10	=	- 1
   	12		15		6		60		60

   
   Since the result (or net effect) is negative, hence tank would be emptied.
   

   So, 1/60 is emptied in 1 hour 3/4 would be emptied in	1	×	3	= 45 hours
   	1/60		4

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