Two pipes, when working one at a time, can fill a cistern in 3 hours and 4 hours, respectively while a third pipe can drain the cistern empty in 8 hours. All the three pipes were opened together when the cistern was 1/12 full. How long did it take for the cistern to be completely full?

- a)2 hours
- b)1 hour 45 minutes
- c)2 hour 11 minutes
- d)2 hour 10 minutes

Correct answer is option 'A'. Can you explain this answer?

Related Test: SSC CHSL Mock Test -10

Knowledge Hub
answered
Jun 26, 2020

Let the total amount of work in filling a cistern be 24 units. (LCM of 3, 4 and 8)

⇒ Work done by pipe 1 in 1 hour = 24/3 = 8 units.

⇒ Work done by pipe 2 in 1 hour = 24/4 = 6 units.

⇒ Work done by pipe 3 in 1 hour = 24/ (-8) = -3 units

⇒ Total work done in 1 hour = 8 + 6 – 3 = 11 units

∴ Time required to complete 11/12^{th} of the work = 11/12 × 24/ 11 = 2 hours

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Two pipes, when working one at a time, can fill a cistern in 3 hours and 4 hours, respectively while a third pipe can drain the cistern empty in 8 hours. All the three pipes were opened together when the cistern was 1/12 full. How long did it take for the cistern to be completely full?a)2 hoursb)1 hour 45 minutesc)2 hour 11 minutesd)2 hour 10 minutesCorrect answer is option 'A'. Can you explain this answer? over here on EduRev! Apart from being the largest SSC community, EduRev has the largest solved
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