If we look at past RBI Grade B Phase 1 exams, Time & Work questions appear regularly in the Quant section. You can expect 4 to 6 questions on Time and work questions in DI or Arithmetic. That is around 13 to 20% of the Quantitative Aptitude section. The questions are moderately difficult. But the trick is to solve them fast without making silly mistakes. In this blog, you will not only get the most important formulas but also learn quick calculation methods that toppers use to fetch full marks in it. Read on to get the best examples and sample questions to master this part of the Quant section.
ALSO READ: How to Score Maximum Marks in Cloze Test
What Is Time & Work?
Time & Work measures how quickly work gets done. It tells you how much work one person (or more) can complete in a certain time. Pipes & Cisterns are just the same idea, only with water filling or emptying tanks.
Important Formulas You Must Know
Learn these by heart. Use them until they become automatic.
- Work Formula
Work = Rate × Time.
- Rate
Rate = 1 / Time taken to finish 1 unit of work.
Example: If a person finishes work in 5 days, Rate = 1/5 work per day.
- Combined Work Rate
If A’s rate = 1/x and B’s rate = 1/y,
together: Rate = (1/x + 1/y).
- Pipes & Cisterns
Same formula as above.
If one fills and the other empties: Rate = (Fill rate – Empty rate).
- Work Done in k Days
Work done = k × Rate.
Common Question Types
In RBI Grade B exams, you’ll see standard Time & Work types like:
- Individual work rate problems
- Combined work rate problems
- Alternate-day work problems
- Efficiency ratio problems
- Pipes & Cisterns (related topic)
Each has a pattern. If you know the method, solving them takes less than a minute. The good thing is the questions don’t change much year to year.
5 Smart Tricks to Save Time
Learning tricks is not about shortcuts without logic. It’s about knowing the fastest way that still gives the right answer. Once you learn the unitary method, LCM method, and ratio method, most questions become easy. These methods cut down the number of steps, so you work faster. You must practice them daily.
LCM Method
The LCM method is the fastest for Time & Work. Find the LCM of total work units, divide by each person’s time to get their work rate, and then solve in one or two steps. This method works for most question types. Once you get used to it, you’ll rarely go wrong.
Ratio Method
The ratio method is helpful for efficiency-based questions. Convert work rates into ratios, then solve without writing too many steps. It’s a great method when you have multiple workers and changing conditions. Practice it with old RBI Grade B papers to build speed and accuracy.
Here are the fastest ways to handle these questions in the RBI Grade B Phase 1 exam:
1. Always Convert to “1 Day Work”:
Instead of counting total work each time, find how much work one person does in 1 day.
Example:
A finishes work in 6 days → Rate = 1/6 per day.
B finishes work in 8 days → Rate = 1/8 per day.
Together = 1/6 + 1/8 = (4 + 3) / 24 = 7/24 work/day.
2. Use LCM for Faster Calculation:
When numbers are big, take LCM of days to get total work in “units”.
Example:
A = 6 days, B = 8 days.
LCM = 24 units.
A = 4 units/day, B = 3 units/day, together = 7 units/day.
Time to finish 24 units = 24/7 days.
3. For Pipes & Cisterns, Subtract Rates:
If one pipe fills in 5 hours and another empties in 10 hours:
Fill rate = 1/5, empty rate = 1/10.
Net = 1/5 – 1/10 = (2 – 1) / 10 = 1/10 tank/hour.
4. Handle “Part Work” Carefully:
If work stops midway, calculate the work done in that period. Subtract from total.
Example:
A and B together = 12 units/day.
Work needed = 36 units.
They work 2 days → 24 units done.
Remaining = 12 units.
5. Use Proportion Logic for Faster Answers:
If a person works twice as fast, time taken becomes half. This shortcut is useful when speed changes are given.
ALSO READ: How to Score Maximum Marks in Cloze Test & Ratio & Proportion Concepts
Practice Examples
Example 1:
A finishes work in 4 days, B in 6 days.
Together in 1 day = 1/4 + 1/6 = (3 + 2)/12 = 5/12 work.
Total time = 12/5 days = 2.4 days.
Example 2:
A fills a tank in 8 hours, B empties in 12 hours.
Net rate = 1/8 – 1/12 = (3 – 2) / 24 = 1/24 tank/hour.
Time = 24 hours.
Example 3:
A, B, C complete work in 10, 12, and 15 days.
LCM = 60 units.
A = 6/day, B = 5/day, C = 4/day.
Together = 15 units/day.
Time = 60 / 15 = 4 days.
Example 4:
Pipe A fills in 5 hours, Pipe B in 6 hours, Pipe C empties in 10 hours.
Net = 1/5 + 1/6 – 1/10 = (6 + 5 – 3)/30 = 8/30 = 4/15 tank/hour.
Time = 15/4 hours = 3 hours 45 minutes.
How to Master Time & Work for RBI Grade B Phase 1 exam?
If you want to solve Time and work questions quickly, you should:
- Practise 1-day work method daily.
- Always check units, like days, hours, minutes.
- Keep LCM tricks ready for clean numbers.
- For Pipes & Cisterns, keep looking for the “emptying” sign.
- Don’t skip simple ratio shortcuts for speed.
How to Practise Well
Start with 5 to 6 questions daily. Mix normal work problems and Pipes & Cisterns. It’s important to time yourself while practicing. Target for 45 seconds for every question. Plus, do note down every mistake in a small notebook. Revise them at night. After a week, answer all those questions in which you made mistakes until you get all right.
Daily Mini Task
- Solve 2 normal Time & Work problems.
- Solve 2 Pipes & Cisterns problems.
- Learn or revise one trick.
Do this for 10 days in a row.
Takeaway
Time & Work questions can be your fastest marks in RBI Grade B Phase 1. The formulas are simple. The tricks save seconds. Once you master the 1-day work method, LCM approach, and net rate logic, you can solve any type, including Pipes & Cisterns, in under a minute. Treat these like quick wins in the exam. Practice is the way to succeed. Write down your mistakes. Repeat the same question until you get it right without looking at the solution. By exam day, you will handle these questions with confidence and speed.
Are you preparing for the RBI Grade B exam 2025? If so, it’s the ideal time to start and accelerate your exam preparation. The notification can be released anytime soon!
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FAQs
Usually 4 to 6.
1-day work method with LCM.
Yes, just with water flow instead of labour.
Yes, for speed when rates change.
About 7–10 days of regular practice.
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