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
Pipe A 20min 3L LCM =60L/5
Pipe 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
Pipe A -2hours -3L LCM 6L/5L=1 1/5hrs.
Pipe B -3hours -2L = 6L
Combined Efficiency -5L
(Minus sign is only for indication purpose that tank is empting)
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
Pipe A 3hours 4L LCM 12L/1L=12hrs
Pipe B -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
Pipe A 4hours 1L LCM 4L/1L=4hrs
Pipe B -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
Pipe A -40min -1L LCM =40L/5
Pipe B -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.)