Time and Work for RRB PO 2025, Check How to Solve Them Easily

The Time and Work topic is one of the most important and frequently asked sections in the Quantitative Aptitude part of banking exams like RRB PO 2025. Mastering this topic is important as it frequently appears in both prelims and mains exams. This question tests your ability to logically understand relationships between time, efficiency, and work completion rates. In this article, we are providing the detailed & important concepts, formulas, shortcut tricks, and some most expected questions for time and work questions to help you ace this topic effortlessly.

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Here we are providing the IBSP RRB PO Topic test for the reasoning and quant sections. Candidates can click the link below and attempt the questions.

What is Time and Work?

In simple terms:

• Work refers to a job or task to be completed.
• Time is the number of days or hours taken to complete the work.
• Efficiency is the rate at which a person or machine can complete a job.

These three elements are interconnected:

Work = Time × Efficiency

Important Formulas for Time and Work

Before diving into problem-solving, let’s recall some key formulas:

Basic Formulas:

1. Work Done in 1 Day = 1 / Total Days
2. Total Work = Efficiency × Time
3. If A can do a work in ‘x’ days, and B can do the same work in ‘y’ days, then together they can do the work in:

1. Efficiency Ratio:
   

If A can do a work in ‘x’ days and B in ‘y’ days, then their efficiency ratio is:

1. If A is ‘n’ times as efficient as B, then: Time taken by A : 

Time and Work Important Questions For RRB PO 2025

Here we are providing the time and work important questions for the RRB PO 2025 exam, Candidates can check the important questions PDF along with the detailed solutions in the article below.

Question 1: ‘A’ can complete 40% of a work in 16 days. ‘B’ is 25% less efficient than ‘C’. ‘C’ takes 16 days less than ‘A’ to complete the work. In how many days ‘A’ and ‘B’ together can complete 84.375% of the work together.

A) 12 days

B) 15 days

C) 10 days

D) 18 days

E) 20 days

Question 2: (A + 10) men can complete a project in 24 days working 6 hours a day, while (A + 6) men can complete the same project in 20 days working 8 hours a day. Find the time taken by 20 men to complete the same work working 9 hours a day.

A) 36 days

B) 28 days

C) 32 days

D) 24 days

E) 30 days

Question 3: B is 20% more efficient than A, who is 50% more efficient than C. If A, B and C together can complete a piece of work in 45 days, then find the time taken by B alone to complete 72% of the total work.

A) 77.4 days

B) 77.8 days

C) 78.4 days

D) 76.2 days

E) None of these

Question 4: A, B and C can complete a piece of work in 63 days, 72 days and 84 days respectively. If A and B started doing the work together and worked on it for 20 days then find the time in which C will complete the remaining work.

A) 36 days

B) 32 days

C) 24 days

D) 34 days

E) None of these

Question 5: ‘A’ can complete a work in 48 days while ‘B’ can complete the same work in 36 days. If ‘A’ worked with 200% more efficiency and ‘B’ worked with 25% less efficiency, then find the number of days taken by both of them to complete the work together.

A) 9 days

B) 18 days

C) 15 days

D) 10 days

E) 12 days

Candidates should download the PDF to access more questions and detailed solutions.

Types of Time and Work Problems

1. Individual Work: Calculating the time taken by one person to complete a task.
2. Combined Work: Determining the time taken when multiple people work together.
3. Work with Different Efficiencies: Comparing workers with varying speeds.
4. Pipes and Cisterns: A variation where pipes fill or empty tanks, similar to work rates.
5. Work with Breaks or Partial Work: Accounting for interruptions or incomplete tasks.
6. Man-Days Concept: Total work is measured as the product of the number of workers and days.

Key Formulas

1. Basic Formula:
   • Work = Rate × Time
   • Rate = Work / Time
   • Time = Work / Rate
2. Combined Work:
   • If A completes a job in ‘a’ days and B in ‘b’ days, their combined work rate is (1/a + 1/b) per day.
   • Time taken together = (a × b) / (a + b) days.
3. Efficiency:
   • Efficiency is inversely proportional to time. If A takes 4 days and B takes 6 days, their efficiencies are in the ratio 1/4: 1/6 = 6:4 = 3:2.
   • Total work can be calculated using the LCM of the days to represent the total work units.
4. Pipes and Cisterns:
   • Filling pipe: Positive work rate (e.g., 1/10 tank per minute).
   • Emptying pipe: Negative work rate (e.g., -1/15 tank per minute).
   • Combined rate = Sum of individual rates.

Easy Methods to Solve Time and Work Questions

To solve Time and Work problems quickly for RRB PO 2025, use these approaches:

1. LCM Method for Total Work

• Find the LCM of the days taken by individuals to represent the total work.
• Example: A takes 6 days, B takes 8 days. LCM(6, 8) = 24 units (total work).
• A’s efficiency = 24/6 = 4 units/day, B’s efficiency  = 24/8 = 3 units/day.
• Combined efficiency of A and B = 4 + 3 = 7 units/day.
• Time taken by them = (24/7) = 3(3/7) days.

2. Combined Work Formula

• For two workers A and B with times ‘a’ and ‘b’ days:
  • Time together = (a × b) / (a + b).
• Example: A takes 10 days, B takes 15 days.
  • Time together = (10 × 15) / (10 + 15) = (150/25) = 6 days.

3. Efficiency Ratio Method

• Convert time to efficiency using the inverse relationship.
• Example: A takes 5 days, B takes 10 days. Efficiency ratio = 10:5 = 2:1.
• Total work = LCM(5, 10) = 10 units.
• A’s efficiency = 2 units/day, B’s efficiency = 1 unit/day.
• Combined rate = 3 units/day, so time = 10 / 3 ≈ 3.33 days.

4. Pipes and Cisterns

• Treat filling pipes as positive rates and emptying pipes as negative rates.
• Example: Pipe A fills a tank in 10 hours, Pipe B empties it in 15 hours.
  • Combined rate = (1/10) – (1/15) = (3 – 2)/30 = (1/30) tank/hour.
  • Time to fill = 30 hours

5. Man-Days Concept

• Total work = Number of workers × Days.
• Example: 5 workers complete a job in 12 days. How long for 10 workers?
  • Total work = 5 × 12 = 60 man-days.
  • Time for 10 workers = 60 / 10 = 6 days.

Tips for RRB PO 2025

• Practice LCM-Based Problems: Most Time and Work questions use LCM to standardize work units.
• Memorize Common Fractions: Know fractions like 1/6, 1/8, 1/12 to quickly calculate efficiencies.
• Simplify Calculations: Use approximations for speed in prelims but ensure accuracy in mains.
• Check for Negative Work: In pipes and cisterns, account for emptying pipes.

Time Management: Skip complex problems initially and return if time permits.

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