Work-Rate Problems – When Total Work is Defined on GMAT

50-Word Summary

Define total work in man-hours: men × days × hours. Convert mixed teams to a common unit (e.g., men-equivalents). Set old man-hours equal to new man-hours, then solve for unknown days or hours. This reduces work-rate problems to a single equation and prevents unit mistakes.

Overview

Work-rate problems are among the most practical and logical question types on the GMAT. They test your ability to break down a situation into manageable parts and calculate how long a task will take when multiple people or groups contribute. In your GMAT prep course, the key for such problems is to always define the total work in terms of man-hours or man-days, depending on the setup of the problem. This allows you to translate the effort of men, women, or even groups with different efficiencies into a single comparable unit.

For example, if 10 men working 12 hours a day can complete a task in 20 days, the total effort is expressed as 10 × 20 × 12 man-hours. Any new arrangement of workers must equal this same total work. Such questions are not just about calculations but about clarity of method, which is crucial for solving GMAT Quantitative Reasoning problems confidently.

 

Defining Total Work in Man-Hours

A common type of GMAT question involves calculating work efficiency across different groups. Consider the question:

10 men take 20 days to complete a task, working 12 hours a day. How many days will 6 men working 10 hours a day take to finish the same task?

The first step is to define the total work in terms of man-hours:
10 men × 20 days × 12 hours = 2400 man-hours.

Now assume the new group takes K days. Their total contribution would be:
6 men × K days × 10 hours = 60K man-hours.

Equating the two:
60K = 2400

→ K = 40.

Thus, the new group would take 40 days to finish the task.

 

For thorough practice on full-length tests, check out our 15 GMAT mock tests

 

Handling Different Efficiencies

Now consider a variation:

10 men take 20 days working 12 hours a day to finish a task. A new team consists of 20 women and 30 children. It is given that 20 women are equivalent to 40 men in efficiency and 30 children are equivalent to 10 men. If they have 16 days to complete the work, how many hours per day must they work?

Step 1: Define the total work.
10 × 20 × 12 = 2400 man-hours.

Step 2: Convert the new team into men-equivalents.
20 women = 40 men, 30 children = 10 men, so total = 50 men.

Step 3: Express the work equation.
50 × 16 × H = 2400, where H is hours per day.

Solving gives H = 3.

Therefore, the new team only needs to work 3 hours per day.

Why This Method Matters

These problems look simple, yet on the GMAT they evaluate disciplined reasoning. Defining total work in man-hours gives one common unit to compare different team sizes, hours, and efficiencies. The approach speeds setup and reduces mistakes under pressure. Rehearse it in a free GMAT full-length mock test to confirm unit consistency and timing, and you will carry greater clarity and confidence into work-rate questions.

Parting Thought

Defining total work as one teaches a larger lesson: decide the whole, then let every minute serve it. Progress gathers when effort is measured, combined, and aligned. In GMAT preparation, treat each study block as a fraction of a clear objective, add reliable routines, and watch time convert into results. In the b-school application process, unify essays, recommendations, resume, and interviews under one coherent purpose so every hour invested strengthens the same total. In life, energy is finite; define the work that matters and invite others when shared effort raises the combined rate. Clarity of the whole makes each part meaningful.