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Lessons in this course 0/6 All courses Aptitude for Placements

Placements

Progress0 / 6 lessons
  1. 1. Percentages and the shortcuts
  2. 2. Ratio, proportion and partnership
  3. 3. Averages, alligation and mixtures
  4. 4. Time, speed, distance, trains and boats
  5. 5. Time and work with the men-days method
  6. 6. Profit, loss and discount

Courses › Aptitude for Placements

Time and work with the men-days method

The LCM trick that removes fractions, and the men-days proportion.

15 min read · Lesson 5 of 6 · Pro

Rate is the whole idea

If A finishes a job in 10 days, then in one day A finishes 1/10 of it. That fraction is A's rate. Rates add: two people working together have a combined rate equal to the sum of their rates.

Working with fractions like 1/12 + 1/18 is slow and error-prone under time pressure. So use the trick below instead.

The LCM method — use this

Step 1. Take the total work as the LCM of the given days. Step 2. Each worker's efficiency = total work / that worker's days. Step 3. Add or subtract efficiencies as the story requires. Step 4. Days = total work / combined efficiency.

Every number stays a whole number.

The rest of this lesson is Pro

The free lessons of Aptitude for Placements finish what they start — read those first if you have not. This one goes further, and it is part of the paid half.

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