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CAT Time, Work & Pipes Questions
Practise time, work & pipes (quantitative aptitude) for the Common Admission Test: 10 multiple-choice questions, each with the correct answer and a worked explanation. Click an option to check it, or “New questions” for another set.
Time, Work & Pipes practice
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Q1.Pipe A fills a tank in 10 hours and pipe B empties it in 15 hours. If both are opened, the tank fills in:
Show answer & explanation
Answer: C — 30 hours
Net rate = 1/10 − 1/15 = 5/150 of the tank per hour → 150/5 = 30 hours.
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Q2.Pipe A fills a tank in 6 hours and pipe B empties it in 9 hours. If both are opened, the tank fills in:
Show answer & explanation
Answer: C — 18 hours
Net rate = 1/6 − 1/9 = 3/54 of the tank per hour → 54/3 = 18 hours.
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Q3.A can finish a job in 15 days and B in 10 days. Working together, how long will they take?
Show answer & explanation
Answer: A — 6 days
Work per day = 1/15 + 1/10 = 25/150; together = 150/25 = 6 days.
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Q4.A can finish a job in 12 days and B in 24 days. Working together, how long will they take?
Show answer & explanation
Answer: D — 8 days
Work per day = 1/12 + 1/24 = 36/288; together = 288/36 = 8 days.
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Q5.A can finish a job in 12 days and B in 4 days. Working together, how long will they take?
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Answer: D — 3 days
Work per day = 1/12 + 1/4 = 16/48; together = 48/16 = 3 days.
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Q6.Pipe A fills a tank in 8 hours and pipe B empties it in 12 hours. If both are opened, the tank fills in:
Show answer & explanation
Answer: D — 24 hours
Net rate = 1/8 − 1/12 = 4/96 of the tank per hour → 96/4 = 24 hours.
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Q7.A can finish a job in 20 days and B in 30 days. Working together, how long will they take?
Show answer & explanation
Answer: B — 12 days
Work per day = 1/20 + 1/30 = 50/600; together = 600/50 = 12 days.
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Q8.A can finish a job in 18 days and B in 36 days. Working together, how long will they take?
Show answer & explanation
Answer: B — 12 days
Work per day = 1/18 + 1/36 = 54/648; together = 648/54 = 12 days.
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Q9.Pipe A fills a tank in 20 hours and pipe B empties it in 30 hours. If both are opened, the tank fills in:
Show answer & explanation
Answer: A — 60 hours
Net rate = 1/20 − 1/30 = 10/600 of the tank per hour → 600/10 = 60 hours.
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Q10.Pipe A fills a tank in 12 hours and pipe B empties it in 20 hours. If both are opened, the tank fills in:
Show answer & explanation
Answer: C — 30 hours
Net rate = 1/12 − 1/20 = 8/240 of the tank per hour → 240/8 = 30 hours.
How to approach time, work & pipes questions
Turn each rate into work per day (1/10 of the job per day) or use the LCM of the days as total work. Pipes that empty count as negative work.
About CAT
Common Admission Test — conducted by Indian Institutes of Management (convening IIM rotates). The entrance exam for IIM MBA programmes, with VARC, DILR and Quantitative Ability sections.
Original practice questions written for this site in the style and difficulty of each exam’s syllabus. They are not past papers and the site is not affiliated with any exam body. Exam patterns, marking schemes and syllabi change — always check the latest official notification.
CAT practice topics
| Topic | Section | Question source |
|---|---|---|
| Percentages | Quantitative aptitude | Calculated (new numbers every set) |
| Ratio, Ages & Mixtures | Quantitative aptitude | Calculated (new numbers every set) |
| Time, Work & Pipes | Quantitative aptitude | Calculated (new numbers every set) |
| Algebra | Mathematics | Calculated (new numbers every set) |
| Geometry & Mensuration | Mathematics | Calculated (new numbers every set) |
| Data Interpretation | Data interpretation | Calculated (new numbers every set) |
| Verbal Reasoning & Analogies | Reasoning | Calculated + question bank |