CUET-General Aptitude-16/03/2025

Dear Students, We welcome you in our CUET-General Aptitude-16/03/2025.

Our today’s post is on Pipes and Cisterns as below:

Q 3553) Two pipes A and B can fill a tank in 20min and 30min, separately. If both pipes are opened together, then in how many time the tank will be filled?

(A) 8min  (B) 10min  (C) 12min (D) 13min

Ans: (C) 12min

Solution:

Pipe  Time taken  Efficiency of Pipes Capacity of Tank  Time=TW/TE

A           20min                  3L                        LCM                 =60L/5

B            30min                  2L                         60L                  =12min

Combined Efficiency           5L

( Here Time T means the time taken to fill up the tank  and Efficiency means the measurement of the liquid filled up in tank  in one unit time. It is calculated by dividing  capacity of tank by time taken to be filled up the tank. Total Efficiency or TE: 5L and Total Work or TW: 60L. TW is the LCM of 20 and 30. LCM means the figure, which is divisible by both 20 and 30)

Time taken or T, when both pipes are opened =Total Work or TW/ Total Efficiency or TE

( Formula used for calculatting Efficiency= TW/Time taken. Incase Inlet pipe we use +Efficiency and in Outlet pipe -Efficiency.)

Q 3554) Two taps can empty a full tank in 2 hours and 3 hours respectively. If both are turned on simultaneously, in how many hours will the full tank be emptied?

(A) 1hr  (B) 1 1/2hrs    (C) 1 1/4hrs    (D) 1 1/5hrs

Ans: (D) 1 1/5hrs

Solution:

Pipe              Time         Efficiency    Capacity      Time=TW/TE

P             -2hours          -3L              LCM          6L/5L=1 1/5hrs.

Q             -3hours          -2L              = 6L

Combined Efficiency        -5L

(Minus sign is only for indication purpose that tank is empting)

Other Questions:

Q 3555) Pipe A can fill a tank in 3 hours and Pipe B can empty that tank in 4 hours. If they are opened together then how much time will they take to fill the tank?

(A) 12hrs    (B) 13hrs    (C) 14hrs    (D) 16hrs

Ans: (A) 12hrs

Solution:

Pipes           Time         Efficiency    Capacity       Time=TW/TE

First          3hours            4L             LCM          12L/1L=12hrs

Second    -4hours          -3L             =12L

Combined Efficiency        1L

Q 3556) Tap A can fill a tank in 4 hours while tap B can empty it in 2 hours. If they opened together then how much time will they take to emplty a filled tank?

(A) 2hrs    (B) 3hrs    (C) 4hrs    (D) 6hrs

Ans: (C) 4hrs

Pipe              Time         Efficiency    Capacity     Time=TW/TE

X              4hours            1L             LCM          4L/1L=4hrs

Y             -2hours           -2L             =4L

Combined Efficiency         -1L

Q 3557) A pipe can empty a tank in 40min. A second pipe with diameter twice as that of the first pipe also attached with the tank to empty it. The two together can empty the tank in how much time? …… (CUET UG 2023)

(A) 8min  (B) 10min  (C) 13 min (D) 13 1/3min

Ans: (A) 8min

Solution:

Pipe          Time            Efficiency   Capacity  Time=TW/TE

C           -40min                -1L          LCM              =40L/5

D          -10min                – 4L           40L               =8min

Combined Efficiency           -5L

(Important Note: Whene diameter twice, than area of a cross-section becomes 4 times. Therefore, second pipe empty the tank in 40/4=10min.)

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General Aptitude

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