Quantitative Aptitude
Time & Work
Time & Work
Time & Work problems quantify how fast people or machines complete tasks. If A finishes a job in n days, A's one-day work is 1/n. Combined rates add together. Pipes & Cisterns follow the same logic with fill (positive) and drain (negative) rates.
Key Idea
Use the LCM method: assume total work = LCM of all given days. Each person's daily work becomes an integer, eliminating fractions entirely.
Core Formulas
Work Rate
One day's work of A = 1 / (number of days A takes alone)
First step in any Time & Work problem — convert days to rate.
Two people together
Time together = (A × B) / (A + B)
When only two people work together and you need the combined time.
Efficiency ratio
If A is k times efficient as B → A takes (1/k) the time of B
When relative efficiency is given instead of actual days.
M × D × H = Constant
M1 × D1 × H1 = M2 × D2 × H2
When comparing two scenarios with different numbers of workers, days, or hours.
Pipe fill / drain net rate
Net fill time = (F × D) / (D − F) where F = fill time, D = drain time
When one pipe fills and another drains simultaneously.
Relevant Exams
Time & Work appears in every banking exam (IBPS PO/Clerk, SBI PO) and SSC CGL. Pipes & Cisterns is a direct sub-type tested separately in harder papers.