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TNPSC time and work practice questions with worked answers

By the PrepMatic team · Updated 9 Oct 2026 · 4 min read

Time and work is a pattern-recognition topic. Once you see that "work per day" is the only quantity you need, most questions reduce to adding or subtracting fractions. TNPSC lists it in the aptitude syllabus for Group 4, and the questions are almost always at the level of the five below. The subject guide is TNPSC aptitude and mental ability.

What this topic covers

• Individual and combined work: one worker, two workers, and workers who join or leave.
• Man-days: how the number of workers and the number of days trade off.
• Partial work: a worker completes part of a job and another finishes it.
• Pipes and tanks: the same logic, with taps that fill and drains that empty.

Sample questions

Question 1

A can complete a piece of work in 10 days and B in 15 days. Working together, they will complete it in:

• A. 5 days
• B. 12.5 days
• C. 6 days
• D. 25 days

Question 2

A can do a piece of work in 12 days. A and B together can do it in 8 days. B alone can do it in:

• A. 24 days
• B. 20 days
• C. 30 days
• D. 36 days

Question 3

8 men can complete a work in 15 days. In how many days can 12 men complete the same work, working at the same rate?

• A. 8 days
• B. 12 days
• C. 22.5 days
• D. 10 days

Question 4

A can complete a job in 20 days. He works for 4 days and leaves. B finishes the remaining work in 12 days. B alone can do the whole job in:

• A. 12 days
• B. 15 days
• C. 20 days
• D. 24 days

Question 5

A tap fills a tank in 6 hours, and a drain empties the full tank in 12 hours. If both are opened together, the empty tank will be filled in:

• A. 12 hours
• B. 4 hours
• C. 8 hours
• D. 18 hours

Answers and explanations

1. C. A does 1/10 of the work a day and B does 1/15. Together: 1/10 + 1/15 = 3/30 + 2/30 = 5/30 = 1/6 per day, so they need 6 days.
2. A. Together they do 1/8 per day and A does 1/12, so B does 1/8 − 1/12 = 3/24 − 2/24 = 1/24 per day. B alone takes 24 days.
3. D. The total work is 8 × 15 = 120 man-days. With 12 men: 120 ÷ 12 = 10 days. More men means fewer days, so the answer must be less than 15.
4. B. In 4 days A does 4 ÷ 20 = 1/5 of the work. The remaining 4/5 takes B 12 days, so B does 1/15 per day, and the whole job takes B 15 days.
5. A. Net filling per hour = 1/6 − 1/12 = 2/12 − 1/12 = 1/12. The tank fills in 12 hours. The drain slows the filling, but the tap is stronger, so the tank does fill.

How to prepare time and work

Teach yourself the "total work" shortcut. Choose the total work as the LCM of the given days and express each person's rate as whole units per day. For question 1, take the work as 30 units: A does 3 units a day and B does 2, so together they do 5 units a day and finish 30 units in 6 days. This avoids fractions and makes mental arithmetic faster.

Practise four categories. The first is two workers together. The second is one worker with help from a third. The third is "worker leaves in the middle", as in question 4. The fourth is pipes and tanks, which includes leaks. When a drain is present, subtract; when a tap is present, add.

Use a sanity check for every answer: the combined time must be shorter than either individual time. If your answer for two helpers is longer than one of them alone, you inverted a fraction.

For efficient calculation of totals, see TNPSC LCM and HCF practice, and for inverse relationships between men and days, TNPSC ratio and proportion practice.

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