TestUstad

A cistern has two taps which fill it in 12 min. and 15 min.respectively There is one outlet pipe in the cistern. When all the taps & pipe are opened, the empty cistern is full in 20 min. How long will the waste pipe (outlet) take to empty the full cistern ?

Correct answer: A. 10 min

  • A. 10 min
  • B. 20 min
  • C. 30 min
  • D. 40 min

Explanation

The two inlet taps fill at 1/12 + 1/15 = 3/20 cistern per minute, while the net rate with the outlet open is 1/20 cistern per minute. Thus the outlet rate is 3/20 - 1/20 = 1/10 cistern per minute, so it empties the cistern in 10 minutes. The likely mistake is 20 minutes, which treats the net filling time as the outlet's emptying time.

Written and checked by , MS Computer ScienceLast updated
Report an error

The more specific you are, the faster it gets fixed. A source beats an opinion.

Prefer email? [email protected]

About Time and Work

Problems measure work through rates, treating each person's or machine's contribution as work completed per unit time. Questions cover combined work, efficiency, wages, alternate working schedules, pipes and cisterns, and men-days relationships, with care needed to distinguish time taken by one worker from the time required when workers act together.

Practise Arithmetic

1,060 free Arithmetic MCQs from Mathematics, each with the correct answer and an explanation. Unlimited attempts, no account needed.

Start a free Arithmetic testAll Arithmetic MCQs

Discussion

Stuck on an option, or know a faster way to get there? Ask or explain it here.

No comments yet. Be the first to explain this one.

Exams that ask Mathematics questions like this

Mathematics is on 76 papers prepared for on TestUstad, and all of them draw the same bank, so this question is worth knowing for every one of them.

Lecturer Mathematics Test Mathematics80 MCQsNET Mathematics80 MCQsSubject Specialist Mathematics Test Mathematics80 MCQsATS Mathematics30 MCQsCA QAT Mathematics30 MCQsCTS Mathematics30 MCQsECAT Mathematics30 MCQsETEA Engineering Admission Test Mathematics30 MCQsETEA Recruitment Tests Mathematics30 MCQsGAT General Mathematics30 MCQsGIKI Mathematics30 MCQsNAT Mathematics30 MCQsNED Mathematics30 MCQsNTS Mathematics30 MCQsOTS Mathematics30 MCQsPIEAS Mathematics30 MCQsPTS Mathematics30 MCQsSTS Mathematics30 MCQsUTS Mathematics30 MCQsBCAT Mathematics25 MCQsISSB Mathematics25 MCQsCSS MPT Mathematics20 MCQsPAF Mathematics20 MCQsPAF Airman Mathematics20 MCQsPakistan Army Commissioned Officer Test Mathematics20 MCQsPakistan Navy Test Mathematics20 MCQsPatwari Test Mathematics20 MCQsPMA Long Course Test Mathematics20 MCQsPMD Mathematics20 MCQsComputer Operator Test Mathematics15 MCQsDEO Mathematics15 MCQsEducators ESE Test Mathematics15 MCQsEducators SESE Test Mathematics15 MCQsEducators SST Test Mathematics15 MCQsFBR Mathematics15 MCQsJEST Mathematics15 MCQsJunior Clerk Test Mathematics15 MCQsLAT Mathematics15 MCQsNADRA Mathematics15 MCQsPST Mathematics15 MCQsSub Registrar Test Mathematics15 MCQsAJKPSC Mathematics10 MCQsAssistant BS-16 Test Mathematics10 MCQsBPSC Mathematics10 MCQsECP Mathematics10 MCQsFIA Mathematics10 MCQsFPSC Mathematics10 MCQsGBPSC Mathematics10 MCQsIB Mathematics10 MCQsIntelligence Officer Mathematics10 MCQsKPPSC Mathematics10 MCQsMES Mathematics10 MCQsNAB Mathematics10 MCQsNational Highways and Motorway Police Test Mathematics10 MCQsPakistan Railways Recruitment Test Mathematics10 MCQsPCS Mathematics10 MCQsPIA Mathematics10 MCQsPPSC Mathematics10 MCQsPunjab Police ASI Test Mathematics10 MCQsPunjab Police Sub Inspector Test Mathematics10 MCQsSNGPL Mathematics10 MCQsSPSC Mathematics10 MCQsSub Engineer Civil Test Mathematics10 MCQsSub Engineer Electrical Test Mathematics10 MCQsSub Engineer Mechanical Test Mathematics10 MCQsTehsildar and Naib Tehsildar Test Mathematics10 MCQsWAPDA Mathematics10 MCQsANF Mathematics5 MCQsASF Mathematics5 MCQsCTD Mathematics5 MCQsElite Police Force Test Mathematics5 MCQsPakistan Army Soldier Test Mathematics5 MCQsPakistan Rangers Test Mathematics5 MCQsPERA Force Test Mathematics5 MCQsPunjab Police Constable Test Mathematics5 MCQsRescue 1122 Test Mathematics5 MCQs

More Time and Work questions

6 men and 8 women can complete a work in 10 days. 26 men and 48 women can finish the same work in 2 days. 15 men and 20 women can do the same work in_______days.

P is 30% more efficient than Q. P can complete a work in 23 days. If P and Q work together, how much time will it take to complete the same work?

P works twice as fast as Q. If Q alone can complete a work in 12 days, P and Q can finish the work in________days

To fill a cistern, pipes P, Q & R take 20, 15 & 12 minutes respectively. The time in minutes that the three pipes together will take to fill the cistern is:__________?

A alone can finish a work in 10 days and B alone can do it in 15 days. If they work together and finish, then out of a total wages of Rs.75. A will get:___________?

2 men and 12 women can finish a job in 4 days. 4 men and 6 women can do the same job in 5 days. Find the time taken by 1 man and 1 woman to complete the job.