Time & Work
Time and Work is a core topic in Quantitative Aptitude that measures how fast a person or group can finish a task. The basic principle is that work done is the product of time spent and the rate of working. We call this rate 'efficiency'. If a person is very fast, they take less time to complete a task. If they are slow, they take more time. This shows an inverse relationship between time and efficiency.
Concepts (3)
This concept is used when a group of people works together. It assumes that more men will finish a job in fewer days. If the number of people increases, the time taken decreases proportionally. This is also called the Chain Rule.
This concept is used when a group of people works together. It assumes that more men will finish a job in fewer days. If the number of people increases, the time taken decreases proportionally. This is also called the Chain Rule. It is useful for problems involving workers, hours per day, and different amounts of work. For example, if 10 men build a wall in 5 days, then 1 man would take 50 days.
This method simplifies work into units. Instead of taking work as 1, take the LCM of all given time periods as the total work. For example, if A takes 10 days and B takes 20 days, let total work be 20 units (LCM of 10 and 20).
This method simplifies work into units. Instead of taking work as 1, take the LCM of all given time periods as the total work. For example, if A takes 10 days and B takes 20 days, let total work be 20 units (LCM of 10 and 20). A's daily work is 2 units and B's is 1 unit. Together they do 3 units a day. This avoids using fractions and makes the math simple.
In these problems, people do not work together. Instead, Person A works on day 1, Person B works on day 2, and they repeat this cycle. To solve this, find the total work done in one full cycle (usually 2 days).
In these problems, people do not work together. Instead, Person A works on day 1, Person B works on day 2, and they repeat this cycle. To solve this, find the total work done in one full cycle (usually 2 days). Divide the total work by this cycle's work to find how many full cycles are needed. Then calculate the remaining work for the next individual's turn.
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Start Lesson: Man-Days Concept