Shortcut Techniques to Solve Time & Work Problems in Seconds!
- rahulsirclasses1
- Oct 6, 2025
- 5 min read
Master CAT Quants by Solving Faster and with 100% Accuracy
Time & Work questions are a staple in the CAT Quants section, and they are easy to score—**if you know the shortcuts.** But if you stick to basic equations and long-winded calculations, you might end up losing precious minutes that could be better spent elsewhere in the exam.
At Rahul Sir Classes, we believe in empowering you with efficient problem-solving methods. That's why we teach powerful shortcut techniques from our trusted Quants book—so you can solve these questions faster and with 100% accuracy for CAT 2025.
These techniques are used by toppers to save 3–5 minutes per section—and you can too. Ready to make Time & Work your high-scoring advantage? Let’s dive in!
1. Efficiency Method: The Power of Per-Day Work
This method focuses on the amount of work done by an individual or a group in a single unit of time (e.g., one day, one hour). It's the most fundamental shortcut.
Concept: If a person completes a job in 'D' days, their efficiency (work done per day) is $\frac{1}{D}$.
Application: When multiple people work together, their individual efficiencies can be directly added to find their combined efficiency.
If A takes 10 days and B takes 15 days to complete a work:
A's efficiency = 1/10 work per day
B's efficiency = 1/15 work per day
Combined efficiency= 1/10 + 1/15= (3 + 2) / 30= 5 / 30= 1/6 work per day
Time taken when working together= 1 ÷ (1/6)= 6 days
2. LCM Method: Assuming Total Work for Simplicity
This is a highly effective method that avoids fractions, making calculations much cleaner.
Concept: Assume the total amount of work to be the Least Common Multiple (LCM) of the number of days taken by each individual/group. This ensures that the 'work done per day' for each person is an integer.
Application: If A takes 10 days and B takes 15 days:
LCM of 10 and 15 is 30.
Assume Total Work = 30 units
A's efficiency = 30 units ÷ 10 days = 3 units/day
B's efficiency = 30 units ÷ 15 days = 2 units/day
Combined efficiency = 3 + 2 = 5 units/day
Time taken together = 30 units ÷ 5 units/day = 6 days
3. Work & Wages Logic: Distributing Earnings Fairly
This concept is an extension of the efficiency method, applied when wages are involved. Wages are always distributed in the ratio of the work done by each person.
Concept: If multiple people work on a task and get paid, their share of the wages is directly proportional to the amount of work they individually complete.
Application: If A and B work together for a total of Rs. 1000, and A does $\frac{2}{5}$ of the work while B does $\frac{3}{5}$ of the work, then:
A's share = (2/5) × 1000 = Rs. 400B's share = (3/5) × 1000 = Rs. 600
This also implies that if they work for the same duration, wages are distributed in the ratio of their efficiencies.
4. Negative Work: When Work Gets Undone
Not all work is constructive! Sometimes, an entity works against the completion of the task (e.g., a leak in a tank, a person destroying what others build).
Concept: Treat the efficiency of the 'negative worker' as a subtraction.
Application: If Pipe A fills a tank in 10 hours (efficiency = $\frac{1}{10}$), and Pipe B empties it in 15 hours (efficiency = $-\frac{1}{15}$), then the net efficiency when both are open is:
Net efficiency = $\frac{1}{10} - \frac{1}{15} = \frac{3-2}{30} = \frac{1}{30}$ work/hour.
Time taken to fill the tank = 30 hours.
5. Alternate Day Work: Identifying Cycles
These questions involve individuals working on alternate days. The key is to identify the work done in a complete cycle of days.
Concept: Calculate the total work done in one complete cycle (e.g., 2 days if A works on day 1 and B on day 2). Then, determine how many such cycles are needed to complete the work.
Application: A does 10 units/day, B does 8 units/day. They work on alternate days, A starting first. Total Work = 100 units.
Day 1: A works (10 units)
Day 2: B works (8 units)
Work in 2-day cycle = $10 + 8 = 18$ units.
Number of full cycles for 100 units: $\frac{100}{18} = 5$ cycles with a remainder of 10 units.
Work done in 5 cycles = $5 \times 18 = 90$ units.
Days taken for 5 cycles = $5 \times 2 = 10$ days.
Remaining work = $100 - 90 = 10$ units.
On Day 11, A starts again. A can do 10 units. So A completes the remaining 10 units on Day 11.
Total days = $10 + 1 = 11$ days.
Unlock Your Quants Potential with Time & Work Shortcuts!
Time & Work is a highly scoreable topic in CAT Quants, provided you approach it with the right tools. By mastering these shortcut techniques—Efficiency Method, LCM Method, Work & Wages, Negative Work, and Alternate Day Work—you can significantly reduce your solving time and boost your accuracy.
These methods are not just about speed; they are about understanding the underlying logic that makes problems fall apart quickly. Integrate them into your practice, and watch your confidence soar for CAT 2025!
Ready to Master Time & Work Shortcuts?
Join Rahul Sir Classes today for comprehensive Quants coaching, advanced shortcut techniques, and personalized mentorship to ace CAT 2025.
FAQs
Q1. Which Time & Work method is best for CAT?
The LCM method is generally preferred as it avoids fractions and simplifies calculations, especially when dealing with multiple individuals or varying work rates. However, understanding the Efficiency method is fundamental as the LCM method is derived from it.
Q2. Do Time & Work questions appear frequently in CAT?
Yes, Time & Work, along with Time, Speed, and Distance, are consistently high-weightage topics in CAT Quants. Mastering these concepts and their shortcuts is crucial for a good score.
Q3. How can I practice these shortcuts effectively?
After learning a shortcut, immediately apply it to a variety of practice questions. Start with basic problems and gradually move to CAT-level questions. Time yourself to ensure you're gaining speed. Review solutions to understand optimal application.
Q4. Are there any common traps in Time & Work questions?
Yes, common traps include confusing individual work with combined work, misinterpreting "and" vs. "or" in compound statements, and incorrect handling of negative work or alternate day scenarios. Careful reading and systematic application of shortcuts help avoid these.
Q5. Does Rahul Sir Classes provide specific Time & Work practice?
Yes, Rahul Sir Classes offers dedicated Quants modules covering Time & Work in depth, with numerous practice questions, sectional tests, and detailed video explanations of these shortcut techniques to ensure complete mastery.
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