Infographics: Time and Work

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Time and Work
Master one of the most important topics in quantitative aptitude with this 
comprehensive visual guide to Time and Work concepts, formulas, and 
solving techniques.
Core Concept
Work is proportional 
to time taken. 
Efficiency and time 
are inversely 
proportional when 
total work remains 
constant.
Efficiency Formula
Efficiency ? 1/Time 
taken. If A 
completes work in 
'n' days, then A's 
one day work = 1/n
Three Methods
Unitary Method, 
Percentage 
Capacity, and LCM 
Approach (most 
efficient for 
competitive exams)
Three Powerful Approaches
01
Percentage Approach
Total work = 100%. If A 
does work in 'a' days, 
then in one day A does 
100/a% of work. Simple 
for mental calculations.
02
LCM Method (Best)
Take LCM of given days 
as total work. Calculate 
individual efficiency by 
dividing LCM by days. 
Most efficient for 
competitive exams.
03
Work Equivalence
Work = Work Rate × 
Time. When work 
doubles, the product 
(Work Rate × Time) also 
doubles. Powerful for 
complex problems.
Example: LCM Method
Pr oblem: A can do work in 10 days, 
B in 12 days. How many days 
together?
Solution:
LCM(10,12) = 60 units (Total 
work)
1.
A's efficiency = 60/10 = 6 
units/day
2.
B's efficiency = 60/12 = 5 
units/day
3.
Combined = 11 units/day 4.
Time = 60/11 = 5.45 days 5.
Negative Work Concept
When someone builds and another 
destroys simultaneously, treat 
destruction as negative work.
F or mula: Work per day = 1/a - 1/b = 
(b-a)/ab
Ex ample: Amit builds wall in 6 
hours, Rohit destroys in 10 hours. 
Together: 1/6 - 1/10 = 1/15, so 15 
hours needed.
Essential Formulas Reference
1
Basic Formula
M¡D¡/W¡ = M¢D¢/W¢
Men × Days for Work¡ = Men × 
Days for Work¢
2
With Work Hours
M¡D¡T¡/W¡ = M¢D¢T¢/W¢
Including hours per day in 
calculation
3
With Efficiency
M¡D¡T¡E¡/W¡ = M¢D¢T¢E¢/W¢
Complete formula with all 
parameters
4
Two Persons Working
Time = (xy)/(x+y) days
When A finishes in x days, B in y 
days
5
Three Persons Working
Time = (xyz)/(xy+yz+zx) days
When A, B, C finish in x, y, z days
6
Individual Time
B alone = xy/(y-x) days
When A+B take x days, A alone 
takes y days
Pipes & Cisterns: Special Application
Pipes and cisterns problems use the same Time & Work concepts. Inlet 
pipes do positive work (filling), while outlet pipes do negative work 
(emptying).
Inlet Pipes
Pipes that fill the tank. 
Their work is 
considered positive. 
Rate = Tank capacity / 
Time to fill
Outlet Pipes
Pipes that empty the 
tank. Their work is 
considered negative. 
Rate = -Tank capacity / 
Time to empty
Combined Working
Net rate = Sum of inlet 
rates - Sum of outlet 
rates. Use LCM method 
for quick solutions.
Important Pipes & Cisterns Formulas
Leak Time Formula
If a pipe takes x 
minutes normally but 
y extra minutes due to 
leak:
Leak empties in = (x² + 
xy)/y minutes
Tank Capacity
Leak empties in a 
hours, pipe adds b 
litres/hour, tank 
empties in c hours:
Capacity = (a×b×c)/(c-a) 
litres
Diameter Relation
Rate of flow is 
proportional to square 
of diameter:
Rate ? d²
If diameter doubles, 
rate becomes 4 times
Key Proportionality Rules
More Men
³ Fewer Days
± More Work
More Days
± More Work
³ Fewer Men Needed
More Efficiency
³ Less Time
± More Work Done
Solved Example Walkthrough
Problem: Contractor's Dilemma
A contractor employs 100 workers to complete work in 100 days. 
After 50 days, only 1/3 work is completed. How many more workers 
needed to finish on time?
Analyse Given Data
100 men × 50 days = 1/3 work 
completed. Remaining work = 2/3, 
Remaining time = 50 days
Calculate Work Done
If 100 men complete 1/3 in 50 
days, then to complete 2/3 work 
in same time, we need 
proportionally more men
Apply Formula
M¡D¡/W¡ = M¢D¢/W¢
100×50/(1/3) = M¢×50/(2/3)
M¢ = 200 men
Find Additional Men
Additional men = 200 - 100 = 100 
more workers needed
Practice Problem Strategy
40%
Identify Method
Choose LCM for 
multiple workers, 
percentage for simple 
ratios
30%
Set Up Equation
Write the relationship 
clearly before solving
30%
Calculate & Verify
Double-check your 
answer makes logical 
sense
Common Mistakes to Avoid
Forgetting to subtract outlet/leak rates
Not converting different time units properly
Missing the "together" vs "alone" distinction
Calculation errors in fractions
Not considering efficiency variations
Success Mantra
"Practice 50+ problems using LCM method. Master formula 
application. Time and Work contributes 4-6 questions in SSC CGL4
make them your scoring zone!"
Summary: Master Time & Work
3
Solution Methods
Unitary, Percentage, 
and LCM approaches
6
Core Formulas
Essential formulas to 
memorise completely
4
Question Types
Basic, pipes-cisterns, 
negative work, 
efficiency
Time and Work is a scoring topic in SSC CGL when you understand the core 
concepts and apply the right method. The LCM approach is your best friend 
for speed and accuracy. Remember: Efficiency × Time = Constant Work. 
Master the formulas, practise diverse problems, and watch for common 
exam tricks. With consistent practice, you can achieve 100% accuracy in this 
topic!