Time and Work - Complete Guide for SSC
Time and Work Concepts
Time and Work deals with calculating work done, time taken, and efficiency of workers.
Key Principle: If A can do work in n days, then A’s 1 day work = 1/n
Essential Formulas
1. Basic Work Formula
Work = Time × Efficiency
If A does work in 'a' days: A's 1 day work = 1/a
If B does work in 'b' days: B's 1 day work = 1/b
Together: (A+B)'s 1 day work = 1/a + 1/b
2. Efficiency and Time (Inverse Relation)
Efficiency ∝ 1/Time
If A:B efficiency = 2:3
Then A:B time = 3:2 (reciprocal)
3. Combined Work
If A completes in 'a' days and B in 'b' days:
Together they complete in: (a×b)/(a+b) days
4. Work and Wages
Wages ∝ Work Done ∝ Efficiency × Time
If A and B work together:
Wage ratio = Efficiency ratio = Work done ratio
Solved Examples
Example 1: Basic Time and Work
Question: A can do work in 12 days and B in 15 days. How long will they take together?
Solution:
A's 1 day work = 1/12
B's 1 day work = 1/15
Together = 1/12 + 1/15 = (5+4)/60 = 9/60 = 3/20
Days required = 20/3 = 6⅔ days
Answer: 6⅔ days
Example 2: Efficiency Problem (SSC Favorite!)
Question: A is twice as efficient as B. A takes 6 days less than B. Find B’s time.
Solution:
Let B takes x days
Then A takes (x-6) days
Efficiency ratio A:B = 2:1
Time ratio A:B = 1:2
(x-6)/x = 1/2
2(x-6) = x
2x - 12 = x
x = 12 days
Answer: B takes 12 days
Example 3: Advanced Problem (Difficult)
Question: A and B together can complete a work in 12 days. A alone can complete it in 20 days. In how many days can B complete 60% of the work?
Solution:
A + B = 12 days
A = 20 days
B = ?
1 day work of A + B = 1/12
1 day work of A = 1/20
1 day work of B = 1/12 - 1/20 = (5-3)/60 = 2/60 = 1/30
So B takes 30 days to complete full work
For 60% work: 60% of 30 = 0.6 × 30 = 18 days
Answer: 18 days
Important Shortcuts
Shortcut 1: LCM Method
Take LCM of all days → Assume total work Calculate daily work → Find answer
Shortcut 2: Efficiency Ratio
If efficiency ratio = a:b Time ratio = b:a (inverse)
Difficulty-Based Practice
Easy Level (For Beginners)
- Basic work-time problems
- Simple efficiency questions
- Direct formula application
Medium Level (For SSC CHSL/MTS)
- Combined work problems
- Efficiency ratio questions
- Pipes and cisterns basics
Hard Level (For SSC CGL)
- Complex work scenarios
- Advanced efficiency problems
- Multi-stage work processes
Related Topics
Additional Resources
💡 Pro Tip: Time and Work concepts are similar to Time and Distance. Master both together!
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